Manipulating the fundamental properties of light at the nanoscale represents a new paradigm of modern optics. Controlling polarization states on-demand, for example, is highly desirable in optical communications, bio-imaging and quantum information processing, where fast continuous switching, compactness, and ease of integration are essential. In this regard, anisotropic 2D quantum materials like black phosphorus (BP) provide an attractive platform with its electronically tunable anisotropy, strong excitonic absorption and direct bandgap, all at the ultrathin limit of atomic-scale thicknesses.
\r\n\r\nThis thesis explores the capacity of BP for optically efficient, broadband and versatile polarization modulation by integrating the material into a variety of nanostructures. We first examine methods for optically efficient modulation with 2D materials via resonance wavelength detuning and high-Q cavities. By leveraging spatially engineered polarization gradients, we propose a tunable polarization beam splitter demonstrating the potential of BP for structuring light.
\r\n\r\nWe then present a plasmonically-coupled black phosphorus metasurface capable of multispectral polarization control over several telecommunication bands. The device represents a 10-fold decrease in thickness and 5-fold decrease in gating voltage over similar modulators in the literature. Finally, we report a dual-gated cavity integrating two cross-aligned BP layers for comprehensive, all-electronic modulation across the Poincar\u00e9 sphere surface. This is the first demonstration of independent, active two-parameter control via excitonic tuning in an optical cavity.
\r\n\r\nBy concluding with several propositions of multi-dimensional parameter control using 2D quantum materials, this work illustrates the versatility of BP as a modulator, opening further possibilities for the arbitrary structuring of light.
", "doi": "10.7907/pwkz-vm62", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18749", "collection": "thesis", "collection_id": "18749", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012026-203030942", "primary_object_url": { "basename": "MendozaSean2026.pdf", "content": "final", "filesize": 76299073, "license": "other", "mime_type": "application/pdf", "url": "/18749/1/MendozaSean2026.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Toroidal Plasmoid Generation via Extreme Hydrodynamic Shear: Optical and Magnetic Studies", "author": [ { "family_name": "Mendoza", "given_name": "Sean A.", "orcid": "0009-0004-9945-0200", "clpid": "Mendoza-Sean-A" } ], "thesis_advisor": [ { "family_name": "Gharib", "given_name": "Morteza", "orcid": "0000-0003-0754-4193", "clpid": "Gharib-M" } ], "thesis_committee": [ { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Gharib", "given_name": "Morteza", "orcid": "0000-0003-0754-4193", "clpid": "Gharib-M" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "Water is a ubiquitous molecule that mediates our interactions with the world and the dynamics of the universe on scales from astrophysical to biomolecular. Controlling its behavior is an essential step in semiconductor manufacturing and water purification. While commonly viewed as a conductive medium, pure water is in fact quite a good insulator, with a resistivity of \u03c1 \u2248 18 M\u03a9 cm. Such purity is typically short-lived; however, water of sufficient purity allows for unique interactions with solid media as a result of its strong polarization and high dielectric strength (\u03b5 \u2248 80, dipole moment \u03c1 \u2248 3 D). In contact with normal glass, this leads to electric double layer buildup, where the substrate's superficial atoms -oxygen, typically- preferentially adsorb the polarized hydrogen atoms of the water molecules, resulting in the generation of an electrical potential known as contact electrification. If the fluid is further accelerated against the glass, this effect is amplified via a charge-ripping process whose exact nature is still debated.
\r\n\r\nIn this work, we examine a specific result of this contact electrification and triboelectrification process via the impingement of a high-speed jet of pure water, normal to dielectric substrates - mainly quartz glass and lithium niobate - with velocities up to 250 m s-1. We observe a velocity-dependent electric field which, at a critical threshold of approximately 120 m s-1, exceeds the breakdown threshold for electrical discharge in air (\u2248 3 MV m-1), resulting in the formation of a toroidal plasma. We show that the condition of the water, e.g. its resistivity, is essential for this phenomenon, and that the intense shear resulting from this impingement is the primary driver of electrification. By changing the ambient gas to helium or argon, a near-complete shift in the optical spectrum is observed, demonstrating that this is mainly a gas-phase phenomenon.
\r\n\r\nWe further investigate the case of argon, which shows an anomalous pale blue luminescence, and determine that the majority of the visible luminescence in the case of argon is a result of bremsstrahlung radiation, i.e. the deceleration of electrons on impact with argon neutrals, and that a symmetric toroidal core near the jet annulus - functionally a cathode - corresponds to a region of elevated electron temperature within a roughly 10 \u00b5m radial extent of the jet surface. The near-perfect symmetry of this interior core, along with the elevated electron energy, suggests that the energy and the symmetry may be related.
\r\n\r\nGiven the non-thermal nature of this plasma, we estimate that a magnetic field of up to approximately 290 mT would be required to balance the nitrogen electron pressure (nekBTe \u2248 10-68 kPa). To determine whether this is phenomenologically feasible, we develop an approach for magnetic field measurement at extreme proximity via remote sensing, in which the sensing elements are directly embedded into the dielectric target. A lab-grown diamond with a thin 5 \u00b5m layer of nitrogen-vacancy (NV-) centers allows magnetometry within approximately 75 \u00b5m of the plasma core while requiring no modification to the flow or plasma field. We are able to remotely perform a vector measurement which demonstrates a magnetic field structure consistent with a negatively charged stream of distilled water, and we measure a field strength of up to \u00b11 \u00b5T at a measurement standoff distance of z = -75 \u00b5m, which drops rapidly to about 0.25 \u00b5T after the onset of plasma. Based on the extensive averaging times of this embodiment, we conjecture that this drop is a consequence of the pulsatile behavior of the discharge, with a signal outside of the dynamic range of our detector.
\r\n\r\nWe then develop a simple electrostatic and magnetostatic picture of the electric field and currents. An electric field model is built from the measurements and the proposed charge distribution. Treating the system as a single closed current circuit, the azimuthal magnetic field follows directly from the enclosed current by Amp\u00e8re's law, B\u03b8 = \u00b50 I / (2\u03c0r), with no field where no net current is enclosed.
\r\n\r\nWe consider two currents within this circuit. A weak fluid charging current, O(10 mA) advected with the jet, accounts for the pre-onset field; because our sensor sits outside the enclosed current - where an axisymmetric current produces no field - the \u00b11 \u00b5T we measure reflects the non-axisymmetric part of the distribution. During breakdown a much larger, highly uncertain discharge current (instantaneous peak O(50 A), pulsed at a duty cycle O(10-4), so its time-average matches the charging current) gives a surface field O(100 mT) at the nominal core radius r \u2248 100 \u00b5m, whose magnetic pressure B\u03b82/2\u00b50 (~a few kPa) acts outward, tending to expand the current loop. This magnetic pressure is of the same order as the computed electron pressures (10-68 kPa)- likely weaker, but not negligible - and both act outward, so a self-consistent model of the observed structure must account for both. While a real azimuthal magnetic field accompanies the flow, the stark symmetry of the plasma core is more plausibly set by the impinging-jet stagnation hydrodynamics and triboelectric charging than by the magnetic self-field.
", "doi": "10.7907/7meb-df80", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18692", "collection": "thesis", "collection_id": "18692", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05292026-174801779", "primary_object_url": { "basename": "Thesis_final.pdf", "content": "final", "filesize": 20542830, "license": "other", "mime_type": "application/pdf", "url": "/18692/1/Thesis_final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Multilayer Meta-Optics for Next-Generation Multifunctional Photonics", "author": [ { "family_name": "Baspinar", "given_name": "Ayse Bilgehan", "orcid": "0009-0005-5382-6118", "clpid": "Baspinar-Ayse-Bilgehan" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Optical metasurfaces, planar arrays of subwavelength scatterers that precisely manipulate the amplitude, phase, and polarization of light, have emerged as a compelling platform for next-generation photonic systems. While single-layer passive metasurfaces have demonstrated remarkable optical functionalities, practical applications increasingly demand devices that are dynamically reconfigurable, spectrally multifunctional, and compatible with scalable nanofabrication. This thesis addresses these challenges through the design, fabrication, and characterization of active and multilayer metasurfaces across a diverse set of photonic applications. Active functionality is realized through a nanoelectromechanically tunable architecture based on slot-mode resonances at telecom wavelengths, where an on-substrate design of high-aspect-ratio doped silicon slabs overcomes the fragility of prior suspended structures to achieve low-voltage amplitude and phase modulation and efficient beam steering. A central enabling contribution is a high-throughput direct-write electron-beam lithography platform, in which an antimony precursor decomposes in situ into high-index Sb\u2082S\u2083, eliminating deposition and etching steps and unlocking efficient multilayer fabrication. This platform underpins several advances: three-layer quasi-bound-state-in-the-continuum metasurfaces forming decorrelated filter arrays for compressive hyperspectral imaging that surpass prior implementations; an inverse-designed vertical fiber-to-chip coupler reaching high simulated coupling efficiency without modifying the underlying photonic circuit; and, to our knowledge, the first free-form multilayer meta-optic Bayer color router in the visible spectrum, demonstrating the highest layer count achieved with this platform to date. The work further extends to system-level applications, presenting geometric-phase metasurfaces that serve as phase aberration correctors for optical vortex coronagraphs, validated by Mueller-matrix polarimetry across centimeter-scale apertures, and a planar metamirror that stabilizes a cavity for microwave-to-optical quantum transduction. Together, this thesis establishes a unified framework spanning material and fabrication innovation, dispersion engineering, and inverse design, advancing meta-optics toward scalable, multifunctional photonic systems for real-world applications.", "doi": "10.7907/pcsg-5a08", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18686", "collection": "thesis", "collection_id": "18686", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05292026-044218968", "primary_object_url": { "basename": "Charbonneau_Andrew_Thesis.pdf", "content": "final", "filesize": 36533382, "license": "other", "mime_type": "application/pdf", "url": "/18686/1/Charbonneau_Andrew_Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Advancing Large-Scale Snow Modeling with Data-Driven Parameterizations", "author": [ { "family_name": "Charbonneau", "given_name": "Andrew J.", "orcid": "0009-0004-3269-5713", "clpid": "Charbonneau-Andrew-J" } ], "thesis_advisor": [ { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" } ], "thesis_committee": [ { "family_name": "Thompson", "given_name": "Andrew F.", "orcid": "0000-0003-0322-4811", "clpid": "Thompson-A-F" }, { "family_name": "Schneider", "given_name": "Tapio", "orcid": "0000-0001-5687-2287", "clpid": "Schneider-T" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Deck", "given_name": "Katherine M.", "orcid": "0009-0001-0572-7642", "clpid": "Deck-Katherine-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Snow is a key component of the terrestrial cryosphere, governing surface energy exchange, water storage, and hydrological variability across seasonal to multi-decadal timescales. Despite its importance, snow dynamics remain among the most challenging earth system components to model. This difficulty arises from the strong coupling of microphysical, radiative, and mechanical processes across scales spanning orders of magnitude, from grain-scale metamorphism to global atmospheric circulation. This dissertation develops physics-informed parameterizations for snow depth, albedo, and surface temperature for usage within large-scale snow models. For snow depth and albedo, this work develops and evaluates a hybrid physics-machine learning framework, designed to reconcile the expressive flexibility of data-driven methods with the structural constraints required for physically consistent simulation. The proposed approach embeds physical guardrails directly into a neural dynamical system, enabling small, computationally efficient models to learn nonlinear updates while remaining stable, bounded, and compatible with coupled global climate model architectures. Across both site-level and global-scale evaluations, the developed schemes match or exceed established empirical and process-based parameterizations. This performance extends from the modeled variables to downstream effects like snow season timing, and generalizes across a range of climate types. The hybrid parameterization framework substantially improves generalization compared to unconstrained approaches. Further assessment suggests observational efforts and available training ranges remain critical for further improvement, rather than deficiencies in the modeling framework itself. Overall, this work demonstrates that a hybrid framework --- and the choice of simple, yet flexible structures, instead of detailed but strict formulations --- offers a viable and scalable alternative to traditional snow parameterizations, achieving improved accuracy at reduced cost. Outcomes reinforce the idea that embedding even minimal physical structure into data-driven or basic schemes can yield robust improvements in complicated physical systems.", "doi": "10.7907/am08-6j06", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18685", "collection": "thesis", "collection_id": "18685", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05292026-040935004", "type": "thesis", "title": "Collective Interactions in Cavity-Coupled Rare-Earth Ion Ensembles for Quantum Technologies", "author": [ { "family_name": "Fukumori", "given_name": "Rikuto", "orcid": "0000-0003-0896-4261", "clpid": "Fukumori-Rikuto" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" }, { "family_name": "Choi", "given_name": "Joonhee", "orcid": "0000-0002-3507-8751", "clpid": "Choi-Joonhee" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Rare-earth ions in solids are a promising platform for quantum technologies because they combine atom-like optical and spin transitions with the practical advantages of a solid-state host compatible with optical and microwave resonators. This thesis studies cavity-coupled 171Yb3+ ensembles in oxide crystals as a platform for collective cavity-QED and many-body physics, motivated by the goal of using rare-earth ions as hybrid quantum interconnects for quantum computation and networking. The central theme is that coupling many rare-earth ions to a shared resonator mode creates a rich setting for studying fundamental collective and many-body physics, while also providing a practical route to microwave-to-optical conversion, protected spin storage, and interfaces between superconducting circuits and optical photons.
\r\n\r\nIn 171Yb3+:YVO4, a nanophotonic cavity coupled to an inhomogeneously broadened ion ensemble reveals collective cavity QED in a solid. This work led to the discovery of collectively induced transparency, a cavity-QED phenomenon arising from collective interference in a driven, disordered ensemble. The same system exhibits optical superradiance and subradiance, and supports an interacting microwave spin system in which dipolar exchange competes with disorder, allowing studies of quantum thermalization. With Floquet control, these spin dynamics can be modified to reveal discrete time-crystal signatures. In 171Yb3+:CaWO4, related experiments demonstrate microwave superradiance, one-axis twisting, and many-body gap protection in a solid-state spin ensemble.
\r\n\r\nThese physics results are developed alongside quantum-technology applications. The 171Yb3+:YVO4 platform further enables low-noise microwave-to-optical transduction with percent-level on-chip efficiency and added noise near the single-photon level, establishing rare-earth ensembles as a promising approach to optical interconnects for superconducting quantum systems. In 171Yb3+:CaWO4, cavity-mediated gap protection extends Ramsey coherence and supports the development of a spin-based microwave quantum memory, including a classical-regime demonstration of storage and optical readout. The final part develops the superconducting qubit architecture needed to drive a rare-earth transducer with single microwave excitations, including qubit readout, tunable-coupler SWAP control, and cable-mode characterization. Together, these results establish cavity-coupled rare-earth ensembles as a versatile platform for studying fundamental cavity QED and many-body physics and for developing quantum technologies.
", "doi": "10.7907/4zys-mm04", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18663", "collection": "thesis", "collection_id": "18663", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282026-141341552", "type": "thesis", "title": "Emerging Directions in Active and Multi-Layer Meta-Optics", "author": [ { "family_name": "Gu", "given_name": "Yiran", "orcid": "0009-0001-0283-504X", "clpid": "Gu-Yiran" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391x", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Meta-optics, composed of artificial nanostructures that enable precise control of light, have been widely studied for both fundamental science and technological applications. Compared to conventional bulky optical elements, they offer reduced size, weight, and power consumption, along with enhanced and multifunctional capabilities. As the field enters the transition from fundamental scientific exploration to scalable, real-world technologies, this thesis investigates emerging directions in meta-optics by integrating material and fabrication innovations, dispersion engineering, and inverse design to realize high-performance, scalable optical devices while overcoming key limitations of conventional metasurfaces. Active functionalities are demonstrated using silicon\u2013organic slot metasurfaces, where enhanced light\u2013matter interaction enables low-voltage electro-optic modulation, offering a pathway toward high-speed, CMOS-compatible free-space spatial light modulating devices. A central contribution lies in dispersion-engineered resonances, where concepts such as quasi-bound states in the continuum and band/zone folding are leveraged to achieve spectrally selective, and angle- or polarization-insensitive responses. In parallel, a novel fabrication platform for multilayer, high-index-contrast dielectric meta-optics in the visible regime is developed, enabling precise layer alignment and low-loss operation for volumetric photonic structures. Furthermore, a fabrication-robust inverse design framework is developed to realize compact and 3D photonic interconnects, addressing practical constraints in integrated systems. The advances are further connected to system-level applications through the demonstration of a dielectric metasurface-based coronagraph for space imaging. Together, this work establishes a unified framework for meta-optics that bridges fundamental physics, computational design, and advanced material and fabrication platforms, enabling scalable, multifunctional photonic systems for real-world applications.", "doi": "10.7907/6h0q-5t06", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18444", "collection": "thesis", "collection_id": "18444", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03252026-010757636", "primary_object_url": { "basename": "Sisler_Jared_2026_Embargo.pdf", "content": "final", "filesize": 9990011, "license": "other", "mime_type": "application/pdf", "url": "/18444/9/Sisler_Jared_2026_Embargo.pdf", "version": "v9.0.0" }, "type": "thesis", "title": "Electrically Tunable Optical Active Metasurfaces in Space\r\nand Time", "author": [ { "family_name": "Sisler", "given_name": "Jared", "orcid": "0000-0002-0660-7909", "clpid": "Sisler-Jared" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Controlling the properties of light in space and time is fundamental to many areas of science and engineering. In recent years, actively tunable metasurfaces have enabled dynamic and precise manipulation of the wavefront of light in a compact form-factor, paving the way for a revolution in optics and photonics. This thesis furthers our understanding of such active nanophotonic devices and experimentally presents advanced control over light using two distinct material platforms: indium tin oxide (ITO) and liquid crystals (LCs). The conclusions from this work will enable the design and fabrication of more sophisticated active optical devices.
\r\n\r\nWe start with an introduction to metasurfaces by providing a brief history of their development and the physics of their operation. We then outline the subfield of active metasurfaces and provide the relevant background for the remainder of this thesis.
\r\n\r\nChapter 2 continues with a detailed background on ITO by summarizing its properties, common deposition methods, and methods of characterization. We then provide an in-depth analysis of how the properties of ITO can be changed through annealing in different material environments. This underpins much of the work that is presented in Chapters 3--5 of this thesis.
\r\n\r\nUsing the principles introduced in Chapter 2, we present a method to create precisely defined lateral doping gradients in a thin film of ITO. Our process selectively dopes regions of ITO via patterning a low-quality oxide layer on top of a planar film of ITO, followed by a low temperature (150 \u00b0C) anneal and the removal of the evaporated Al\u2082O\u2083. We fabricate reflective gratings of varying periodicity and demonstrate plasmonic guided modes in an unpatterned film of ITO. This work paves the way for ITO films to be integrated in more complex photonic devices such as on-chip modulators and free-space metasurfaces, as well as furthering our understanding of the material and optical properties of ITO.
\r\n\r\nNext, we demonstrate an ITO-based electrically tunable reflective metasurface in the midwave-infrared (mid-IR). This device operates by electrically modulating the carrier concentration in ITO when placed in a gap plasmon resonator to control the phase and amplitude of scattered light across a surface. Through appropriate electrical and optical design, we demonstrate the polarization-independent tunable diffraction of light in two dimensions (2D). This device represents a significant step forward for solid-state beam-steering devices in the mid-IR which are essential to applications such as thermal imaging and gas sensing.
\r\n\r\nIn Chapter 5, we experimentally show the electrical spatiotemporal modulation of an ITO-based metasurface in the near-infrared (near-IR) for the generation and tunable diffraction of high frequency signals. In this work, we use a similar device design as was used to demonstrate mid-IR beam-steering. We first modulate our device with frequencies up to 10 MHz to generate sidebands offset from the near-IR incident laser frequency. Through temporal waveform engineering, we generate select sidebands of interest and suppress unwanted sidebands. Finally, by spatially varying the time-delay of the temporal modulation, we can diffract --- or normally reflect --- each generated frequency. This device paves the way towards active metasurfaces for multi-beam, multi-frequency functionalities such as free-space optical communication.
\r\n\r\nFinally, we present a highly transmissive active metasurface enabling polarization rotation of near-IR light in 2D using a LC infiltrated titanium dioxide (TiO\u2082) metasurface. Our device consists of a subwavelength periodic array of TiO\u2082 nanopillars submerged in a thin (2 \u03bcm) LC layer and supports electric and magnetic dipole modes. Using a biased photoactive top contact, we spatially control the polarization rotation of transmitted light in 2D through the patterning of a 435 nm pump laser on the surface of the device. This work represents a significant contribution to LC-based optical devices through the detailed modeling of LC interactions with TiO\u2082 nanostructures to enable the efficient modulation of a large-area active metasurface.
\r\n\r\nThis thesis presents many aspects of materials fabrication, characterization, and modeling which are fundamental to the development of the next generation of active photonic devices.
", "doi": "10.7907/qr45-5670", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18761", "collection": "thesis", "collection_id": "18761", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012026-223645069", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 13675713, "license": "other", "mime_type": "application/pdf", "url": "/18761/1/Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Measuring and Characterizing Ultrafast Quantum States Using Nanophotonic Optical Parametric Amplifiers", "author": [ { "family_name": "Sendonaris", "given_name": "Elina Maria", "orcid": "0009-0003-4209-2783", "clpid": "Sendonaris-Elina-Maria" } ], "thesis_advisor": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Photonics offers the potential for large-scale, room-temperature, and ultrafast quantum operations. Multiplexing pulses of light allows for high throughput speeds and dense encoding, with tens of thousands of optical modes being present in a time as short as a microsecond. However, the measurement speed of electronic devices such as photodetectors is currently one bottleneck in such time-multiplexed scalability, because many quantum optical protocols rely on measurement, including state preparation, feed-forward, and feedback. Furthermore, characterization of quantum states and modes is essential for their effective use. Using nanophotonic optical parametric amplifiers (OPAs) presents one way to circumvent the measurement limitations of current quantum photonic schemes. Their large amplification bandwidth, enabled by dispersion engineering on nanophotonic integrated platforms, allows information encoded in femtosecond-scale, THz-bandwidth, multimode quantum optical states to be accessed with nonlinear optical interactions.
\r\n \r\nIn this work, we show how ultra-broadband integrated nanophotonic OPAs can be used to measure ultrafast and multimode quantum states of light. First, we explore the single-photon detection capabilities of OPAs, showing that current OPAs operating in the Gaussian regime are capable of 250 MHz photon count rates with 26% efficiency and a 2% dark count probability. We also show how non-Gaussian operation through pump depletion, with performance that approaches state-of-the-art photon detectors in terms of efficiency and dark count rate while retaining ultrafast operation, can become experimentally possible with a higher nonlinear coupling rate and lower loss. Next, we use nanophotonic OPAs to both generate and characterize multimode ultrafast squeezed vacuum. We use the photocurrent distribution of amplified squeezed vacuum to recover 2.41 dB of squeezing in one mode of a 154-fs multimode squeezed pulse and reconstruct its Wigner distribution. Finally, we investigate the capabilities of broadband nanophotonic OPAs to determine the temporal mode structure and quadrature variances of ultra-broadband temporally multimode quantum states by adapting frequency-resolved optical gating to the quantum regime. We numerically show the successful full characterization of a multimode squeezed state, even in the presence of noise. Together, these results establish OPAs as a valuable measurement device for measuring ultrafast quantum pulses and learning the structure of multimode quantum states, and they provide one building block towards a framework for scalable continuous-variable quantum photonics in which state generation, manipulation, and characterization occur within the same nanophotonic platform.
", "doi": "10.7907/ggz4-5161", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17699", "collection": "thesis", "collection_id": "17699", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09242025-004457327", "primary_object_url": { "basename": "S_Davis_Dissertation-submission.pdf", "content": "final", "filesize": 73936635, "license": "other", "mime_type": "application/pdf", "url": "/17699/1/S_Davis_Dissertation-submission.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Teleportation from Quantum Networks to Traversable Wormholes: the Physics and Technology of Entanglement", "author": [ { "family_name": "Davis", "given_name": "Samantha Isabel", "orcid": "0000-0001-9994-8165", "clpid": "Davis-Samantha-Isabel" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "thesis_committee": [ { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Kitaev", "given_name": "Alexei", "orcid": "0000-0002-5777-642X", "clpid": "Kitaev-A" }, { "family_name": "Hsieh", "given_name": "David", "orcid": "0000-0002-0812-955X", "clpid": "Hsieh-David" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis presents developments in quantum information technologies and their applications to both quantum networks and fundamental physics. It is organized into three parts. Part I focuses on the design and implementation of state-of-the-art sources and detectors for quantum networks. Key contributions include the development of photon-number-resolving superconducting nanowire detectors and their application to heralded single-photon generation and photon-number discrimination; a high-rate multiplexed entangled photon-pair source for quantum key distribution; and on-chip balanced homodyne detectors for the detection of squeezed light. I describe how phased arrays can facilitate wireless quantum communications by introducing the concept of ``quantum phased arrays'' and present the first large-scale optoelectronic phased array receiver on a chip capable of interfacing with nonclassical light, with first demonstrations of coherent imaging and beamforming of squeezed states of light. Part II details the construction of quantum network testbeds at Caltech and Fermilab, designed to realize scalable architectures for the quantum internet. These systems demonstrate high-fidelity quantum teleportation over 45 km of optical fiber and entanglement swapping with time-bin qubits. The experiments are supported by the development of theoretical models that guide system optimization. I also present demonstrations of entanglement distribution at Caltech and remote sites at Fermi and Argonne National Labs with picosecond-level clock synchronization, representing milestones toward the deployment of quantum networking infrastructure across national laboratories. Part III investigates how quantum networks can be used to probe fundamental questions in physics. I report the first experimental generation of GHZ states with time-bin qubits, towards the deployment of multipartite entanglement distribution in real-word networks for tests of quantum mechanics and distributed sensing. Finally, I present the first experimental realization of a traversable wormhole teleportation protocol implemented on a quantum processor, a step in the program of quantum gravity in the lab. I conclude with an outlook and discuss future directions of this work.", "doi": "10.7907/v1zm-yz68", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17730", "collection": "thesis", "collection_id": "17730", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10242025-180540612", "primary_object_url": { "basename": "BLi_Thesis_2025_final.pdf", "content": "final", "filesize": 107553040, "license": "other", "mime_type": "application/pdf", "url": "/17730/1/BLi_Thesis_2025_final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Frequency Stabilization and Frequency Conversion in High-Q Silicon Nitride Microresonators", "author": [ { "family_name": "Li", "given_name": "Bohan", "orcid": "0009-0007-8210-1903", "clpid": "Li-Bohan" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Integrated photonics is an active research field in the recent decade. Silicon nitride is a prominent platform that features low optical loss and can be fabricated in a high-volume complementary metal\u2013oxide\u2013semiconductor (CMOS) foundry. The first part of the thesis focuses on taking advantage of these two mature properties to create integrated lasers with high frequency stability, which possibly has the lowest frequency noise among integrated lasers at the time when this thesis is written. Silicon nitride is also popular in the four-wave-mixing applications as it has an inherent high third-order optical nonlinearity. In the second part of this thesis, however, I present advancement and applications of the second order optical nonlinearity in this material. The second order nonlinearity is not inherent but rather induced by optical signals through photogalvanic effect. This effect is presented as weak historically, but efficient applications are made available in this thesis through the high enhancement of low loss microresonators. Applications include efficient generation of low-noise and tunable lasers through second harmonic generation and demonstrating the quantum nature of correlated photon-pairs generated through spontaneous down conversion.", "doi": "10.7907/nmk6-8s45", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18736", "collection": "thesis", "collection_id": "18736", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012026-154153446", "type": "thesis", "title": "Nanophotonic Lightsail Optomechanics for Long-Range Optical Manipulation and Interstellar Exploration", "author": [ { "family_name": "Gao", "given_name": "Ramon", "orcid": "0000-0003-3591-7209", "clpid": "Gao-Ramon" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Roukes", "given_name": "Michael Lee", "orcid": "0000-0002-2916-6026", "clpid": "Roukes-M-L" }, { "family_name": "Sader", "given_name": "John E.", "orcid": "0000-0002-7096-0627", "clpid": "Sader-J-E" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Laser propulsion, where light serves as fuel based on the principle of photon momentum transfer, might one day allow us to explore other planetary systems. Directing a high-intensity laser beam onto an ultrathin reflective space probe could enable acceleration to relativistic velocities needed for interstellar missions to our neighboring exoplanets within a human lifetime. These laser-driven lightsails, envisioned to be dielectric membranes of square meters in area while weighing at most a few grams, must be prone to shape deformations, withstand laser-induced heating, and harness photon momentum for efficient propulsion and self-correcting dynamics.
\r\n\r\nIn this thesis, we employ optomechanical systems and leverage nanophotonic design principles to address these unprecedented challenges. Importantly, we establish a platform for experimental characterization and model development of laboratory-based lightsail prototypes. We identify silicon nitride membranes as a promising material platform due to its ultralow absorption and fabricate microscopic lightsails based on spring-supported compliant resonators. By using off-resonant collimated laser excitation and noise-robust common-path interferometry while simultaneously operating our device as a micromechanical bolometer, we quantify the propulsive optical force and associated laser power in the linear regime. As we vary the angle of incidence and increase the laser spot size to overfill the lightsail, we reveal noticeable effects of edge scattering on the radiation pressure force --- an observation that represents one of many considerations and lessons to be learned for lightsail development. When driving these tethered lightsails with resonant radiation pressure to micron-scale displacements, nonlinear dynamic behavior emerges due to their geometric nonlinearity. We explore how transitions between bistable mechanical states in the Duffing regime can be controlled with optical forces through noise-mediated sidebands and intermodal coupling.
\r\n\r\nNext, we introduce anisotropically scattering metagratings patterned into silicon nitride membranes as a way to engineer the transfer of light momentum and to generate restoring optical forces and torques for passive stabilization. We characterize the intensity and angular distribution of laser light diffracted from the suspended metagratings versus incidence angle, from which we infer the forces and torques and thus the engineered self-stabilization mechanism. Then, we integrate these metagratings into compliant mechanical resonators optimized for enhanced susceptibility to optical in-plane forces and torques, and describe a route for parallelizing and scaling up fabrication of nanostructured lightsail prototypes. To measure in-plane motion, we propose and implement grating interferometry, whereby interference of two diffracted orders from the metagrating produces fringes that shift as a function of lateral displacement. This allows us to characterize the noise-excited in-plane mode, nanometer-scale translations of and optical in-plane forces on our tethered nanostructured lightsail. Together with our measurements of torsional motion in response to off-centered laser illumination and detected via common-path interferometry, our set of experiments showcase the capabilities of our characterization platform to monitor all motional and rotational degrees of freedom relevant for lightsail dynamics, which paves the way for direct measurement of their associated forces and torques.
\r\n\r\nFinally, we set our sights on the future where our tethered nanostructured lightsails could be brought to the macroscopic domain and released for levitation and propulsion experiments. In particular, we explore the open and critical question of structural deformations by developing a time-domain flight simulator for flexible membranes based on a mass-spring model to study their multiphysics acceleration dynamics. We find that a combination of spin-stabilization and metagrating topology redesigned to account for gyroscopic effects could enable shape stability and beam-riding stability of flat flexible lightsail membranes that are meters in size and subwavelength in thickness.
\r\n\r\nOur numerical and experimental results mark the very beginning of a long-term effort to turn laser-driven lightsails into reality. From a broader perspective, our works seek to advance a complementary avenue in optical manipulation, where complex dynamics and nontrivial optical forces can be achieved by sculpting the material rather than shaping the laser beam. This alternative approach opens the door for controlling the motion of larger objects over longer distances with laser light, which could transform the fields of robotics, manufacturing, spacecraft technology, and interstellar exploration.
", "doi": "10.7907/ehzp-0c84", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18735", "collection": "thesis", "collection_id": "18735", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012026-120746276", "type": "thesis", "title": "Scaling Neutral Atom Tweezer Arrays to 6,100 Qubits", "author": [ { "family_name": "Manetsch", "given_name": "Hannah Jean", "orcid": "0009-0002-3805-3389", "clpid": "Manetsch-Hannah-Jean" } ], "thesis_advisor": [ { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Hsieh", "given_name": "David", "orcid": "0000-0002-0812-955X", "clpid": "Hsieh-David" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical tweezer arrays of neutral atoms have been demonstrated in recent years to be a useful platform for quantum simulation, computation, and metrology. Realizing the full potential of these applications requires increasing qubit numbers while simultaneously maintaining high-fidelity control, which has proved a major challenge across quantum platforms. To date, quantum science experiments have typically been operated with at most hundreds of qubits.
\r\n\r\nIn this thesis, we review the relevant physics of the optical tweezer array architecture and present the technical advances involved in scaling the platform to 6,100 atomic qubits. In tandem with scalability, we demonstrate robust vacuum design, state-of-the-art coherence times, and high single-qubit gate fidelities. To capitalize on the intrinsic connectivity of the architecture at large scale, we investigate long-distance coherent atom transport and briefly describe progress towards two-qubit gate implementation. Finally, we discuss the prospects for scaling the optical tweezer array platform further by an order of magnitude.
", "doi": "10.7907/y7kk-1e96", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17874", "collection": "thesis", "collection_id": "17874", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02072026-200423437", "type": "thesis", "title": "Additive Nanofabrication of 3D TiO\u2082 Metaoptics via Two-Photon Lithography", "author": [ { "family_name": "Chen", "given_name": "Wenyuan", "orcid": "0000-0002-0042-1118", "clpid": "Chen-Wenyuan" } ], "thesis_advisor": [ { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Flat optics based on subwavelength metasurfaces has emerged as a powerful tool for compact and versatile wavefront control, enabling advances in imaging, sensing, displays, and communications. However, the functionality of single-layer metasurfaces is fundamentally limited by the finite degrees of freedom available in a single optical interaction. The growing demand for multifunctionality has motivated innovations in more complex designs involving multilayered structures. While cascaded or multilayer metasurfaces provide this additional design freedom, their realization through conventional top-down lithography is hindered by fabrication complexity and alignment challenges. Additive manufacturing, in particular two-photon lithography, has recently been explored to realize inverse-designed multilayered metaoptics, but such demonstrations have remained largely polymeric. High-index materials fabricated through TPL are still constrained to homogeneous lattices with uniform features. These challenges underscore the importance of alternative fabrication strategies that can expand the design space of multilayer and volumetric structures.
\r\n\r\nIn this dissertation, we establish a bottom-up platform for volumetric metaoptics based on nanoscale additive manufacturing (nano-AM) of TiO2. In Chapter 2, we develop a two-photon lithography framework that overcomes calcination-induced defects, enabling uniformly shrunk TiO2 lattices with lateral dimensions exceeding 90 \u03bcm and thicknesses up to 20 \u03bcm. In Chapter 3, we validate this platform by demonstrating metalenses operating at \u03bb = 4.5 \u03bcm with numerical aperture (NA) up to 0.74. In Chapter 4, we introduce heterogeneous multilayer stacking---achievable in a single lithography step---as a strategy to decouple phase, group delay, and higher-order dispersion control using simple cylindrical unit cells without height constraints. We experimentally realize broadband achromatic metalenses with NA = 0.25 and 0.49, exhibiting near-constant focal lengths across \u03bb = 4-5 \u03bcm. In Chapter 5, we further explore multifunctionality by demonstrating polarization-splitting metalenses and an inverse-designed color router, both fabricated in TiO2. Collectively, this work establishes nanoscale additive manufacturing of high-index oxides as a versatile route to functional multilayer and heterogeneous architectures, complementing existing polymer-based and subtractive approaches, and demonstrating new pathways toward compact, multifunctional, and volumetric optical devices.
", "doi": "10.7907/nyfd-tj09", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17837", "collection": "thesis", "collection_id": "17837", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01262026-214753026", "type": "thesis", "title": "Interfacing Long-Lived Mechanical Oscillators and Superconducting Quantum Circuits", "author": [ { "family_name": "Bozkurt", "given_name": "Alk\u0131m Berke", "orcid": "0000-0003-0633-8902", "clpid": "Bozkurt-Alk\u0131m-Berke" } ], "thesis_advisor": [ { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Mechanical oscillators in the quantum regime hold promise for quantum sensing, frequency conversion and information processing. Because mechanical motion is linear, coupling to an external nonlinear system, such as a qubit, is essential for these applications. Recent advances in piezoelectric interfaces between mechanical oscillators and superconducting qubits have successfully demonstrated precise control of non-classical states of motion. However, challenges associated with heterogeneous integration of piezoelectric materials have limited mechanical quality factors in these systems to around one million, constraining their broader utility.
\r\n\r\nIn this thesis, we explore an alternative approach that harnesses the nonlinearity of electrostatic forces to engineer interactions between superconducting circuits and mechanical oscillators. This strategy allows us to employ mechanical oscillators made of silicon, a non-piezoelectric material with extremely low acoustic loss. We reach the strong coupling regime between a superconducting qubit and a long-lived mechanical oscillator with a quality-factor of around a billion. We employ this system to generate non-classical states of motion that exhibit clear signatures of quantum behavior. Furthermore, we explore the origins of acoustic decoherence and implement strategies to mitigate its impact.
\r\n\r\nThe mechanical lifetimes, which exceed those of best superconducting qubits, open new possibilities for storing and processing microwave quantum information in motional states. Furthermore, our material-agnostic approach is broadly applicable to a variety of material platforms that possess significance for quantum science but lack a piezoelectric response.
", "doi": "10.7907/wz3n-fn09", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17732", "collection": "thesis", "collection_id": "17732", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10262025-132142523", "type": "thesis", "title": "Engineering Quantum Resources for Quantum Networking Using Single Rare-Earth Ions Inside Crystals", "author": [ { "family_name": "Wu", "given_name": "Chun-Ju", "orcid": "0009-0007-0882-4812", "clpid": "Wu-Chun-Ju" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Alicea", "given_name": "Jason F.", "orcid": "0000-0001-9979-3423", "clpid": "Alicea-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Quantum networks are foundational components of quantum technology, enabling transformative applications in secure communication, distributed quantum computation, and enhanced sensing. Rare-earth ions in solid-state hosts represent a leading platform for building such networks due to their exceptional optical and spin coherence properties. This thesis details the experimental realization of a quantum network node using single \u00b9\u2077\u00b9Yb\u00b3\u207a ions in YVO\u2084 coupled to nanophotonic crystal cavities. We demonstrate the fundamental building blocks of quantum networks and develop multiple advanced capabilities, including multiplexing, protected nuclear spin storage, and high-dimensional qudit control, to expand the platform's power and versatility.
\r\n\r\nUsing this platform, we demonstrate heralded remote entanglement between two physically separate devices. A key innovation is a novel entanglement distribution protocol that employs real-time feedforward to cancel spectral diffusion on timescales slower than a single experiment by rephasing the optical transition based on photon arrival time. We also apply real-time phase compensations to entangle \u00b9\u2077\u00b9Yb ions with different optical frequencies. By combining this novel protocol with multiple spectrally distinguishable ions, we demonstrate heralding of a three-ion W state and implement multiplexed remote entanglement. This multiplexing approach increases the entanglement rate by nearly a factor of two, showcasing a scalable pathway to mitigate network overhead.
\r\n\r\nBeyond establishing remote entanglement, we explore the local nuclear spin environment of \u00b9\u2077\u00b9Yb as an integrated quantum resource. We harness the four symmetrically located \u2075\u00b9V nuclear spins to generate multi-qubit Greenberger\u2013Horne\u2013Zeilinger states. Critically, we identify and experimentally verify a decoherence-protected subspace within these states that exhibits insensitivity to common-mode magnetic field noise. By developing a sequence to transfer quantum information into this protected subspace, we establish the \u2075\u00b9VV nuclear ensemble as an integrated, noise-resilient quantum memory.
\r\n\r\nTo further expand the platform's capabilities, we demonstrate coherent control over the four-level ground state of the \u00b9\u2077\u00b9Yb ion, operating it as a qudit. Through development of a new device architecture that enables microwave driving of all transitions and comprehensive characterization of their coherence properties, this work establishes the foundation for higher-dimensional quantum communication protocols that offer significant advantages in network capacity and efficiency.
\r\n\r\nCollectively, these results establish the \u00b9\u2077\u00b9Yb:YVO\u2084 system as a uniquely versatile platform and demonstrate the feasibility of building scalable quantum networks using single rare-earth ions in crystals.
", "doi": "10.7907/kgjp-xe35", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18730", "collection": "thesis", "collection_id": "18730", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012026-040226100", "type": "thesis", "title": "Information Technologies at the Fundamental Physical Limits", "author": [ { "family_name": "Gurses", "given_name": "Baris Volkan", "orcid": "0000-0001-8184-208X", "clpid": "Gurses-Baris-Volkan" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-138", "clpid": "Vahala-K-J" }, { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Fundamental physical laws dictate the performance bounds of all technologies. Over the last century, advances in nanotechnology and integrated circuits have driven the performance of communications, sensing, and computing toward these bounds. As scaling continues, classical limits are increasingly constraining further improvements. The advent of quantum technologies opens paths to overcoming some of these constraints and to building technologies that operate at the fundamental physical limits. This thesis develops a unified framework for these limits and demonstrates large-scale integrated photonic-electronic systems that approach them. In sensing, quantum phased arrays\u2014coherent antenna arrays that transmit or receive quantum fields over free space\u2014are introduced and demonstrated with up to 32 elements for squeezed light imaging, beamforming and beamsteering, overcoming the standard quantum limit to approach the Heisenberg limit and enabling protocols for free-space quantum sensing, quantum communications, and quantum information processing. In communications, quantum coherent transceivers are introduced and demonstrated that transmit and receive non-classical light to surpass the Shannon limit and approach the Holevo limit. In computing, large-scale crosstalk-corrected thermo-optic phase shifter arrays and a 256-element programmable photonic mesh are demonstrated, addressing the scaling challenges of integrated photonic-electronic processors. For each system, I present the underlying theory, design, experiments, and applications, and outline a vision for how these technologies can be practically deployed in the future.", "doi": "10.7907/qhb7-ew96", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:16776", "collection": "thesis", "collection_id": "16776", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10072024-102144911", "type": "thesis", "title": "Microwave Spectroscopy for Probing Electronuclear Modes in Quantum Magnets", "author": [ { "family_name": "Libersky", "given_name": "Matthew Murray", "orcid": "0000-0003-4140-360X", "clpid": "Libersky-Matthew-Murray" } ], "thesis_advisor": [ { "family_name": "Rosenbaum", "given_name": "Thomas F.", "orcid": "0009-0008-6152-666X", "clpid": "Rosenbaum-T-F" }, { "family_name": "Falson", "given_name": "Joseph", "orcid": "0000-0003-3183-9864", "clpid": "Falson-Joseph" } ], "thesis_committee": [ { "family_name": "Motrunich", "given_name": "Olexei I.", "orcid": "0000-0001-8031-0022", "clpid": "Motrunich-Olexei" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Rosenbaum", "given_name": "Thomas F.", "orcid": "0009-0008-6152-666X", "clpid": "Rosenbaum-T-F" }, { "family_name": "Falson", "given_name": "Joseph", "orcid": "0000-0003-3183-9864", "clpid": "Falson-Joseph" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Crystals with rare earth ions present an opportunity to explore a range of model magnetic systems, allowing for an experimental realization of several important physical concepts. For example, the compound LiHoF\u2084 is a transparent, insulating crystal which implements the transverse field Ising model (TFIM) with the Ho\u00b3\u207a spins. The TFIM is a well-known model which is one of the simplest systems to display quantum behavior, such as quantum phase transitions (QPTs). This makes LiHoF\u2084 very useful for investigating these and other quantum effects. LiHoF\u2084 ~also has strong hyperfine coupling to the nuclear spins, which means the excitations must be considered as composite of electronic and nuclear states (i.e., 'electronuclear'). This introduces a nuclear spin bath which modifies behavior near the QPT. In this work, we investigate the behavior of this QPT by probing the electronuclear states in LiHoF\u2084 at microwave frequencies. To accomplish this, we develop the use of loop-gap resonators which enable sensitive microwave measurements in LiHoF\u2084. We also extend the techniques to related systems, such as the 2-dimensional XY antiferromagnet LiErF\u2084. We then investigate ways to observe new phenomena in the LiHoF\u2084 system, namely improving superconducting resonators as one possible way to observe the dynamics of quantum quenching through the QPT.", "doi": "10.7907/n5w4-ae93", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16983", "collection": "thesis", "collection_id": "16983", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02032025-021547979", "primary_object_url": { "basename": "Li_Gordon_2025.pdf", "content": "final", "filesize": 51187093, "license": "other", "mime_type": "application/pdf", "url": "/16983/1/Li_Gordon_2025.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Ultrafast Computing with Nonlinear Photonics", "author": [ { "family_name": "Li", "given_name": "Gordon Han Ying", "orcid": "0000-0001-8184-4915", "clpid": "Li-Gordon-Han-Ying" } ], "thesis_advisor": [ { "family_name": "Marandi", "given_name": "Alireza", "clpid": "Marandi-A" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Bruck", "given_name": "Jehoshua", "orcid": "0000-0001-8474-0812", "clpid": "Bruck-J" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Computers have revolutionized almost every facet of modern society, and as we approach the physical limits of digital electronics, it becomes imperative to investigate alternative computing hardware paradigms to enable the next generation of faster and more energy-efficient computers. This thesis embarks on building the foundation for a new kind of computer, based on ultrafast nonlinear photonics, aiming to overcome some of the limitations plaguing current computers. In particular, we primarily focus on the clock rate, which has stagnated at \u223c5 GHz for conventional microprocessors over the past two decades.
\r\n\r\nWe begin by identifying single nonlinear devices in lithium niobate nanophotonics that can act as essential building blocks for computers, showing a variety of nonlinear functions with operational speeds > 13 THz for artificial intelligence computing workloads. Then, we progress to small-scale photonic computing circuits combining both strong nonlinearity and memory feedback in a physical reservoir computer for temporal information processing with \u223c10 GHz clock rates. Additionally, we explore unconventional computer architectures such as Cellular Automata, which reveals key system-level considerations that maximize the benefits of ultrafast nonlinear photonics in large-scale computers. This culminates in the demonstration of truly end-to-end and all-optical computing with > 100 GHz clock rates, which represents over an order-of-magnitude advancement compared to existing electronic computers. Finally, we prove mathematically how coupled nonlinear optical resonators are Turing-complete computers.
\r\n\r\nOverall, this work builds on the recent advances in nonlinear photonics and highlights a path for a new class of ultrafast photonic computers that can surpass the clock rate and latency limits of electronic computers, hence enabling nascent applications requiring real-time control or information processing at picosecond timescales.
", "doi": "10.7907/g8re-9a27", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17056", "collection": "thesis", "collection_id": "17056", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03122025-171512282", "primary_object_url": { "basename": "Caltech_Thesis_TianXie.pdf", "content": "final", "filesize": 39023176, "license": "other", "mime_type": "application/pdf", "url": "/17056/2/Caltech_Thesis_TianXie.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Scalable On-Chip Platforms for Quantum Microwave-Optical Interface with Solid-State Ensembles", "author": [ { "family_name": "Xie", "given_name": "Tian", "orcid": "0000-0001-6154-1802", "clpid": "Xie-Tian" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Schwab", "given_name": "Keith C.", "orcid": "0000-0001-8216-4815", "clpid": "Schwab-K-C" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Superconducting quantum circuits based on Josephson junctions are one of the most promising platforms for future quantum information processing. Tens of superconducting quantum bits have been integrated on a single chip with performances exceeding the most advanced classical computers. However, these new quantum machines operate at microwave frequencies, which have enormous thermal noise and photon loss at room temperature. This fundamentally limits the future application of this technology in distributed quantum computing and quantum networks. Conversely, optical photons are an ideal information carrier as the photon loss is extremely small in fibers and the thermal noise is negligible at room temperature. Therefore, a quantum transducer that converts between microwave and optical frequencies at the single-photon level is of great importance.
\r\n\r\nThis thesis is centered on building such chip-scale interfaces with rare-earth ion (REI) doped crystals. First, we focus on developing a theoretical understanding of microwave-to-optical transducers. Based on coupled mode theories, we derive a clean theoretical result of the on-resonance transduction model. This allows us to condense the relevant material properties for transduction into a single parameter, effective \u03c7\u207d\u00b2\u207e, describing the strength of the non-linearities provided by the rare-earth ion materials. Next, we designed, fabricated, and measured the chip under cryogenic temperatures, where percent-level efficiency and single-photon level of added noise referred to the input is achieved. To further demonstrate the unique advantage of atom-based platforms, we perform two transducer interference experiments, showing the scalability and capacity towards transducer-assisted remote entanglement of superconducting quantum bits. Lastly, with large microwave cooperativities achieved, we observe novel quantum electrodynamics enabled by controllable initialization of the excited-state spin system. By initializing the spins into spin-down and spin-up states, we observe collectively induced transparency and periodic superradiant emissions, respectively. Simulations are developed to explain the experimental results.
\r\n\r\nThese results establish REI doped crystals as a highly competitive platform for microwave-optical quantum interfaces and pave the way toward remote transducer-assisted entanglement of superconducting quantum machines.
", "doi": "10.7907/03kg-x059", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17193", "collection": "thesis", "collection_id": "17193", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022025-171646095", "type": "thesis", "title": "Electrically Reconfigurable Optical Metasurfaces for Universal Wavefront Shaping", "author": [ { "family_name": "Thureja", "given_name": "Prachi", "orcid": "0000-0003-3852-3395", "clpid": "Thureja-Prachi" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Polman", "given_name": "Albert", "orcid": "0000-0002-0685-3886", "clpid": "Polman-Albert" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The ability to control the properties of light in a compact, reconfigurable platform is essential for advancing nanophotonic technologies. Active metasurfaces --- flat optical components with tunable subwavelength elements --- enable real-time manipulation of wavefronts and thus offer a path toward versatile optical systems. This thesis furthers the development of electrically programmable metasurfaces as a step toward a universal platform for independent and comprehensive wavefront control. By integrating system-level optimization strategies, novel operation modes, and advanced material platforms, we establish a framework for next-generation, on-demand optical processing components.
\r\n\r\nFirst, we introduce an array-level inverse design approach for beam steering metasurfaces, that co-optimizes the spatial amplitude and phase responses to enhance target functionalities. Using the platform of a plasmonic, indium tin oxide (ITO)-based active metasurfaces, we demonstrate non-intuitive configurations that achieve high-directivity, continuous-angle beam steering up to 70\u00b0. Experimental validation confirms the effectiveness of this approach, which we further extend to advanced applications including flat-top beams, tunable beam widths, and multi-beam steering.
\r\n\r\nTo expand the functional channel capacity of active metasurfaces, we then explore space-time modulation as a means of enabling multi-frequency operation. By modulating ITO-based metasurfaces operating at near-infrared wavelengths with tailored waveforms at frequencies up to 10 MHz, we experimentally generate desired frequency harmonics, which appear as sidebands offset from the incident laser frequency. Introducing phase offsets between the driving waveforms enables tunable diffraction of frequency-shifted light. Theoretical extensions of this work highlight the potential of space-time metasurfaces to realize active multitasking components capable of dynamically performing multiple independent functions.
\r\n\r\nFor improved efficiency and broadband operation, we investigate electro-optically tunable metasurfaces based on the Pockels effect in barium titanate (BTO). We develop a scalable fabrication technique to obtain high-quality, thin-film BTO via stress-induced exfoliation from single-crystal substrates, preserving its bulk electro-optic properties. The experimentally measured Pockels coefficient r\u2083\u2083 exceeds that of commercially available thin-film lithium niobate, demonstrating the potential of this material platform for integration into high-speed, low-loss optical metasurfaces. Leveraging these properties, we design transmissive BTO-based metasurfaces for high efficiency beam steering at visible wavelengths.
\r\n\r\nThe results presented in this thesis lay the foundation for next-generation programmable metasurfaces by addressing key challenges in materials, design methodologies, and system-level control architectures. We conclude with a discussion of future directions, including the discovery of high-performance tunable materials, the development of advanced unit cell designs for independent control over multiple optical properties, and the miniaturization of control networks for large-scale metasurfaces. Ultimately, this work advances the development of reconfigurable and intelligent optical systems capable of adapting to diverse technological demands in a broad range of imaging, communication, and computing applications.
", "doi": "10.7907/t5w7-xv05", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17331", "collection": "thesis", "collection_id": "17331", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312025-234853354", "primary_object_url": { "basename": "Ji_Qingxin_2025.pdf", "content": "final", "filesize": 112572969, "license": "other", "mime_type": "application/pdf", "url": "/17331/4/Ji_Qingxin_2025.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Optical Frequency Division Using High-Q Integrated Photonics", "author": [ { "family_name": "Ji", "given_name": "Qingxin", "orcid": "0000-0002-6336-8350", "clpid": "Ji-Qingxin" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Leifer", "given_name": "Stephanie D.", "orcid": "0000-0002-8980-7825", "clpid": "Leifer-Stephanie-D" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical frequency division (OFD) coherently transfers the high spectral purity of optical transitions down to a microwave tone. This coherence transfer makes possible numerous modern technologies, including microwave synthesizing, optical atomic clocks, time and frequency transfer, optical frequency synthesizing, etc. In this thesis, I present advancements in using photonic-chip-based components to perform the OFD with high-performance. Along this pathway, chip-integrated, low-SWaP optical frequency combs are developed using coupled ring resonators. The key features include efficient dispersion tuning using the Moire speedup effect and ultra-high Q factor up to 100 million for an energy-efficient microcomb operation. To illustrate, recording low-noise microwave among those using integrated photonics are demonstrated. In moving towards a deliverable assembly, hybrid system packaging is demonstrated with characterized long-term stability. Ultrafast tuning control using integrated piezoelectric actuation simplifies the system architecture. In particular, an integrated, low-noise PDH locking system, and a full frequency-stabilized microcomb are demonstrated.", "doi": "10.7907/wjew-9m88", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17358", "collection": "thesis", "collection_id": "17358", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022025-065031552", "primary_object_url": { "basename": "KJS_Thesis_red.pdf", "content": "final", "filesize": 5871483, "license": "other", "mime_type": "application/pdf", "url": "/17358/1/KJS_Thesis_red.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Nanophotonic Engineering of Thermal Emitters", "author": [ { "family_name": "Shayegan", "given_name": "Komron Joseph", "orcid": "0000-0002-1532-357X", "clpid": "Shayegan-Komron-Joseph" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Thermal emission is our most ubiquitous light source, as all objects with non-zero temperature emit this type of radiation. Consequently, our ability to shape the spectral and directional properties of thermally emitted and absorbed light by structures is both intriguing at a fundamental level and has practical implications for infrared light sources, radiative cooling, and energy harvesting systems. To impart desired properties to emitted radiation, nanophotonic designs where subwavelength features are patterned into structures have proved effective in preliminary demonstrations of engineered nanoscale control of thermal emission.
\r\n\r\nIn this thesis, we leverage nanophotonic designs to demonstrate new phenomena in the context of thermal emission. We first use a guided-mode structure made of \u03b1-Si to resonantly couple to magneto-optically active InAs. The magneto-optic response is a common effect used in nonreciprocal optical elements, which we use here to directly observe a violation of the Kirchhoff thermal radiation law, a strict equality in the spectral, directional absorptivity and emissivity. This demonstration is significant in two ways: first, it opens new avenues to design thermal emitters with distinct spectral, directional emissivity and absorptivity properties, and second, it confirms theoretical predictions which have long lacked experimental confirmation.
\r\n\r\nWe then extend this experimental Kirchhoff violation to a broadband, directive thermal emitter. The nanophotonic design to achieve this is a deeply subwavelength structure of gradient epsilon-near-zero InAs layers that couple to a Berreman mode. The angular selectivity is determined by the stack thickness, while the broadband spectral range of the effect is imparted by the closely spectrally separated epsilon-near-zero wavelengths.
\r\n\r\nFinally, we theoretically and experimentally lay the groundwork for a thermal lens, where emitted radiation is directed to a focus a given distance above the surface of the structure. Using a combination of coupled dipole approximation, global optimization, and experimental measurements, we realize the necessary collective and local resonance conditions for this effect.
", "doi": "10.7907/1eap-d721", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16428", "collection": "thesis", "collection_id": "16428", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282024-002413905", "primary_object_url": { "basename": "PHDTHESIS.pdf", "content": "final", "filesize": 2457795, "license": "other", "mime_type": "application/pdf", "url": "/16428/1/PHDTHESIS.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Investigation of Quantum Computers for Quantum Simulation and Machine Learning", "author": [ { "family_name": "Kamakari", "given_name": "Hirsh", "orcid": "0000-0002-5377-9631", "clpid": "Kamakari-Hirsch" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Chen", "given_name": "Xie", "orcid": "0000-0003-2215-2497", "clpid": "Chen-Xie" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The use of quantum mechanical phenomena for information processing has the potential to solve computational problems which are believed to be intractable for classical computers. Inspired by this potential, the last several decades has seen rapid development in both the theory and practice of quantum information processing. In this thesis, we explore three applications of quantum computing for the physical and computational sciences.
\r\n\r\nThe first potential application is for the simulation of open quantum systems. We introduce two algorithms for the simulation of open quantum systems governed by a Lindblad equation. Based on adaptations of the quantum imaginary time evolution algorithm, these methods transform non-unitary open system evolution into unitary evolution which can be implemented on contemporary quantum hardware. We demonstrate these algorithms on IBM's quantum hardware via the simulation of the spontaneous emission of a two-level system and the dissipative transverse field Ising model.
\r\n\r\nNext, we explore efficient methods to probe measurement induced phase transitions using superconducting circuits. These phase transitions occur in monitored quantum systems as the measurement rate of randomized single qubit measurements increases. We overcome two exponential bottlenecks which limited the system sizes of previous experiments on superconducting circuits by employing a cross-entropy benchmarking protocol and Clifford based circuit compression techniques. We observed measurement induced phase transitions on systems of up to 22 physical qubits.
\r\n\r\nFinally, we switch our attention to machine learning, where we prove rigorous quantum advantages for adversarially robust classification. By constructing a learning task based on widely accepted cryptographic assumptions, we show a necessary condition for the utility of quantum computers for robust classification. In particular, we show that for the learning task we construct, any efficient classical learner cannot robustly classify better than chance, whereas a quantum learner can efficiently and robustly classify data with high accuracy.
\r\n\r\nThrough these studies, we show that quantum computers have potential application in the physical and information sciences in both the near and long term.
", "doi": "10.7907/rec5-4z30", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16493", "collection": "thesis", "collection_id": "16493", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042024-003837900", "primary_object_url": { "basename": "WU, LUE-Greater than one billion optical Q factor for on-chip microresonators.pdf", "content": "final", "filesize": 14887651, "license": "other", "mime_type": "application/pdf", "url": "/16493/1/WU, LUE-Greater than one billion optical Q factor for on-chip microresonators.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Greater Than One Billion Optical Q Factor for On-Chip Microresonators", "author": [ { "family_name": "Wu", "given_name": "Lue Leo", "orcid": "0000-0002-7503-7057", "clpid": "Wu-Lue-Leo" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is focused on making ultra-high-Q optical microresonators on silicon chips based on design and constructing ultra-low-loss optical waveguides (with losses around 20 dB/km), their fabrication process development, and device applications in on-chip nonlinear optics, including frequency combs, low-noise microwave generation, and narrow-linewidth lasers.
\r\n\r\nFirst, using thermally grown oxide (thermal silica) and wedge microresonator structure, a record Q factor exceeding 1.1 billion is achieved. Then, the limitations of the Q-factor due to surface roughness scattering loss and OH absorption loss are investigated and identified. Absorption limited Q-factor of 8 billion mainly attributed to OH ions is measured. To further explore the potential of thick thermal silica as under cladding material, wedge resonator fabricated in 25-\u00b5m-thick thermal silica achieves a Q-factor of over 60 million, along with a sixfold improvement in thermal stability and a 5 billion absorption-limited Q-factor. Subsequently, low noise microwave signal generation is demonstrated using these devices in a fully optical packaged form, operating soliton microcomb to generate beatnote microwave signals. Noise limitations arising from dispersive waves induced by distinct transverse modes are identified. Additionally, a low-fundamental-linewidth microcavity Brillouin laser is demonstrated, benefiting from device high Q-factor. The noise limits stemming from thermal refractive fluctuation at low offset frequencies and laser output power at high offset frequencies are identified. To improve device integration level, an engineered reduction of interface scattering using TM mode enables a demonstration of 700 million Q factor in a fully-integrated high-aspect-ratio thin SiN platform fabricated in a CMOS foundry. To add one more thing, room temperature soliton microcomb generation is demonstrated for the first time in high-Q AlGaAs microresonators.
", "doi": "10.7907/n1cn-tn34", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16211", "collection": "thesis", "collection_id": "16211", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10202023-123922325", "primary_object_url": { "basename": "PhD_Thesis.pdf", "content": "final", "filesize": 52124772, "license": "other", "mime_type": "application/pdf", "url": "/16211/1/PhD_Thesis.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Single Rare-Earth Ions in Solid-State Hosts: A Platform for Quantum Networks", "author": [ { "family_name": "Ruskuc", "given_name": "Andrei", "orcid": "0000-0001-7684-7409", "clpid": "Ruskuc-Andrei" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Solid-state defects have emerged as leading candidates for quantum network nodes due to their compatibility with scalable device engineering and local nuclear spins for quantum processing. Rare-earth ions in crystalline hosts are particularly attractive due to their long optical and spin coherence times at cryogenic temperatures. However, until recently, detection and utilization of single rare-earth ions in quantum technologies has been hindered by their inherently weak optical transitions. In this thesis I present progress towards realizing a novel quantum network node architecture using single \u00b97\u00b9Yb\u00b3\u207a ions in YVO\u2084, coupled to a nanophotonic cavity.
\r\n\r\nFirst, we demonstrate coherent operation of single \u00b97\u00b9Yb\u00b3\u207a ions as optically addressed qubits. To do this, we leverage first order insensitivity of optical and spin transitions to electric and magnetic fields, thereby protecting the qubits from environmental noise. We demonstrate initialization, high fidelity control and readout of a hyperfine spin qubit with long quantum storage times. We also characterize the optical transitions and find a lifetime-limited echo coherence, thereby enabling a coherent spin-photon interface.
\r\n\r\nNext, we focus on realizing an auxiliary quantum register. The high-fidelity spin control of our \u00b97\u00b9Yb\u00b3\u207a qubit is leveraged to access local nuclear spins. These spins comprise a dense ensemble which serves as a deterministic quantum resource. We utilize Hamiltonian engineering to generate tailored interactions, enabling polarization, coherent control and preparation of many-body nuclear spin states. Finally, we implement a spin-wave based memory protocol and demonstrate storage and retrieval of quantum states.
\r\n\r\nMoving beyond a single quantum node, in the final section of this thesis we will realize a small-scale quantum network using this platform. As a first step we demonstrate time-resolved quantum interference between photons emitted by ions in two separate devices. Then, we demonstrate a novel heralded entanglement protocol which incorporates optical dynamical decoupling and frequency erasure via precise photon detection. This protocol counteracts both static and dynamic inhomogeneity in the ions\u2019 optical transition frequencies, thereby enabling entanglement generation between any pair of qubits in a scalable fashion.
\r\n\r\nThese results showcase single rare-earth ions as a promising platform for the future quantum internet.
", "doi": "10.7907/ecn2-pp53", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16273", "collection": "thesis", "collection_id": "16273", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01032024-012340742", "primary_object_url": { "basename": "How_to_Make_Small_Things_do_Big_Things_for_PDF_v2.pdf", "content": "final", "filesize": 15527558, "license": "other", "mime_type": "application/pdf", "url": "/16273/4/How_to_Make_Small_Things_do_Big_Things_for_PDF_v2.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "How to Make Small Things Do Big Things: Exploring Engineered Disorder for Massively Scalable Metasurfaces and Metamaterials", "author": [ { "family_name": "Wray", "given_name": "Parker Ryan", "orcid": "0000-0003-3384-0826", "clpid": "Wray-Parker-Ryan" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This work presents a collection of topics related to anomalous electromagnetic scattering, emission, and absorption states formed from random systems. The underlying motivation is to explore to what extent metasurface and metamaterial concepts could be applied at a massively large scale; by identifying emergent properties in systems that do not require careful fabrication. Emphasis is placed on exploring theoretical descriptions for systems that do not conform well to existing simpler models. Covered topics include random metasurfaces for spectral filtering and polarization invariance, random nanoparticle films for radiative cooling, broadband polarization and angle invariant absorption using random fractals, effective medium models beyond traditional assumptions, a mathematical transform to understand highly directional scattering/emission in complex systems, and optical metrology and characterization techniques for random systems.", "doi": "10.7907/kvz3-jn93", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16339", "collection": "thesis", "collection_id": "16339", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03222024-181941076", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 192066803, "license": "other", "mime_type": "application/pdf", "url": "/16339/1/Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Quantum Microwave to Optical Transduction with Light-Robust Superconducting Circuits", "author": [ { "family_name": "Wood", "given_name": "Steven Andrew", "orcid": "0009-0004-2582-0627", "clpid": "Wood-Steven-Andrew" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Modern computing and communication technologies such as supercomputers and the internet are based on optically connected networks of microwave frequency information processors. In recent years, an analogous architecture has emerged for quantum networks with optically distributed entanglement between remote superconducting quantum processors, a leading platform for quantum computing. The high coherence, controllability and scalability of microwave frequency superconducting circuits are ideal test-beds for nodes of a quantum network, however, microwave photons are not well suited for transmission of quantum information over long distances due to the presence of a large thermal background at room temperature. Optical photons are ideal for quantum communication applications due to their low propagation loss and negligible thermal occupation at room temperature. Coherent transduction of single photons from the microwave to the optical domain has the potential to play a key role in quantum networking and distributed quantum computing. In this thesis, we present the design of a piezo-optomechanical quantum transducer where transduction is mediated by a strongly hybridized acoustic mode of a piezoacoustic cavity attached to an optomechanical crystal. Our design involves on-chip integration of a light-robust superconducting circuit with the piezo-optomechanical transducer. Absorption of stray photons from the optical pump used in the transduction process is known to cause excess decoherence and noise in the superconducting circuit. The recovery time of the superconducting circuit after the optical pulse sets a limit on the transducer repetition rate. We fabricate niobium nitride based superconducting circuits and test their response to illumination by a 1550nm laser. We find a bandwidth-limited recovery time of $\\sim$ 1us, indicating that a repetition rate exceeding 10kHz should be possible. Combined with the expected efficiency and noise metrics of our design, we expect that a transducer in this parameter regime would be suitable to realize probabilistic schemes for remote entanglement of superconducting quantum processors. We show non-classical microwave-optical photon correlations of the niobium nitride aluminum nitride transducer operated as a spontaneous parametric down conversion source. We go on to show the preparation and characterization of microwave-optical Bell states prepared by the transducer. And finally, we conclude by discussing the challenges with fabricating niobium nitride superconducting circuits and lithium niobate piezoacoustic devices on silicon-on-insulator substrates and provide steps towards realizing our enhanced transducer design.", "doi": "10.7907/kkbj-ex94", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16347", "collection": "thesis", "collection_id": "16347", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04102024-171434556", "primary_object_url": { "basename": "Mi_thesis_final.pdf", "content": "final", "filesize": 42530696, "license": "other", "mime_type": "application/pdf", "url": "/16347/1/Mi_thesis_final.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Many-Body Cavity Quantum Electrodynamics and Spin Dynamics with an Ensemble of Rare-Earth Ions", "author": [ { "family_name": "Lei", "given_name": "Mi", "orcid": "0009-0001-5484-7982", "clpid": "Lei-Mi" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Refael", "given_name": "Gil", "orcid": "0009-0007-4566-8441", "clpid": "Refael-G" }, { "family_name": "Yao", "given_name": "Norman Y.", "orcid": "0000-0003-0194-7266", "clpid": "Yao-Norman-Y" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Studying and controlling light-matter and matter-matter interactions is a central theme in quantum physics and provides the foundation for quantum applications. Rare-earth ions (REIs) doped in solids are promising candidates for engineering scalable quantum technologies, such as quantum memories and quantum transducers, and for exploring emerging fundamental phenomena. This is because REIs have highly stable optical and spin transitions at cryogenic temperatures, and as a solid-state platform, they are compatible for integrating with quantum devices using well-established semiconductor manufacturing techniques.
\r\n\r\nThis thesis is centered on nanophotonic devices coupling to an ensemble of REIs. To explore the light-matter interaction, we build a light-matter interface by coupling an inhomogeneously broadened ensemble of ytterbium-171 doped in yttrium orthovanadate to a nanophotonic cavity with high cooperativity. In this many-body cavity quantum electrodynamics (cavity QED) system, we observe the appearance of a narrow transparency window in the cavity reflection spectrum under optical driving (collectively induced transparency, CIT). This phenomenon results from the destructive interference between pairs of two-level emitters across the inhomogeneous line and the saturation of resonant ions. Furthermore, coherent excitation of the system within this transparency window enables us to observe highly nonlinear optical emission, spanning from fast superradiance to slow subradiance. To study matter-matter interactions, we shift the focus to the strongly interacting spins. These spins feature clock transitions and pure spin exchange interactions, leading to comparable magnitudes of interaction strength and on-site disorder. We characterize and control the many-body dynamics via Hamiltonian engineering and population initialization. Furthermore, we observe the emergence of robust subharmonic oscillations under Floquet driving, providing evidence for the presence of a discrete time crystal.
\r\n\r\nThe discoveries in many-body cavity QED enable new mechanisms for achieving slow light and frequency referencing, and they provide potential for superradiant lasers. Meanwhile, our studies on spin dynamics showcase REIs as a promising platform for the study of many-body physics, with potential applications in quantum sensing and quantum simulations. In general, our findings deepen the understanding for a disordered quantum system and offer valuable insights for development of quantum applications.
", "doi": "10.7907/gx1e-en28", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16164", "collection": "thesis", "collection_id": "16164", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08232023-220808049", "primary_object_url": { "basename": "20230913 - Roberts G - Thesis.pdf", "content": "final", "filesize": 18708521, "license": "other", "mime_type": "application/pdf", "url": "/16164/6/20230913 - Roberts G - Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Design, Realization, and Applications of 3D Multifunctional Nanophotonics", "author": [ { "family_name": "Roberts", "given_name": "Gregory David", "orcid": "0009-0002-0720-3938", "clpid": "Roberts-Gregory-David" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Bruno", "given_name": "Oscar P.", "orcid": "0000-0001-8369-3014", "clpid": "Bruno-O-P" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Metaoptics leverages electromagnetic phenomena and the advanced abilities of modern nanofabrication to replicate traditional optical devices in a fraction of the thickness and to realize novel, compact, multifunctional devices with no known bulk equivalent. Motivated by the expanding role of optics in modern technologies, this field has seen a rise in design techniques for realizing increasingly powerful photonic structures. Three-dimensional (3D) devices, with refractive index distributions patterned at subwavelength scales, represent an enormous design space capable of achieving highly efficient, free space, multifunctional structures. By utilizing a gradient-based, iterative optimization algorithm, a technique for nanophotonic inverse design, we demonstrate scattering structures with unique responses to all the fundamental properties of light. The algorithm is constrained such that resulting devices can be made with realistic multilayer fabrication processes. We present dielectric structures that can be placed directly on top of image sensor arrays and sort light to different pixels based on its wavelength, polarization, and angular momentum, thus enabling efficient and exotic camera technologies. The following work contains fabrication and measurement of 3D devices in the mid-infrared, practical evaluations of devices for visible light imaging applications, and visualizations of underlying structure of photonic design optimization problems.
", "doi": "10.7907/1r1w-0234", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16284", "collection": "thesis", "collection_id": "16284", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01262024-232942660", "primary_object_url": { "basename": "Physics and Applications of Optical Nonlinearity in High-Q Microresonators.pdf", "content": "final", "filesize": 90939906, "license": "other", "mime_type": "application/pdf", "url": "/16284/1/Physics and Applications of Optical Nonlinearity in High-Q Microresonators.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Physics and Applications of Optical Nonlinearity in High-Q Microresonators", "author": [ { "family_name": "Yuan", "given_name": "Zhiquan", "orcid": "0000-0001-9054-6004", "clpid": "Yuan-Zhiquan" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical microresonators trap light in compact volumes at discrete resonant frequencies. Benefiting from the ultra-low propagation loss, the electromagnetic wave intensity is greatly enhanced. Due to the pronounced light confinement, nonlinear optical effects are significantly magnified in the microresonators. In this thesis, I investigate various nonlinear optical phenomena using high quality factor silica wedge and fully-integrated thin film silicon nitride microresonators. The exploration begins with Kerr nonlinearity-induced soliton microcombs followed by their application in mid-IR band gas spectroscopy. The generation of solitons under normal dispersion conditions, which frustrate soliton formation, is then considered. Subsequently, attention is directed towards stimulated Brillouin lasers and their frequency noise performance, including long-term frequency stabilization based on the built-in temperature reference and validation of two modification factors affecting short-term fundamental linewidth. Along this journey, a novel method for calibrating ultra-narrow laser linewidths is introduced. Lastly, this method is employed to measure the narrow linewidth of a visible laser generated through second harmonic generation in silicon nitride resonators.", "doi": "10.7907/vj6e-wr82", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16290", "collection": "thesis", "collection_id": "16290", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02092024-210936211", "type": "thesis", "title": "Quantum Measurements with Superconducting Nanowire Single Photon Detectors", "author": [ { "family_name": "Mueller", "given_name": "Andrew Sterling", "orcid": "0000-0002-6598-9732", "clpid": "Mueller-Andrew- Sterling" } ], "thesis_advisor": [ { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" }, { "family_name": "Shaw", "given_name": "Matthew D.", "clpid": "Shaw-M-D" } ], "thesis_committee": [ { "family_name": "Hutzler", "given_name": "Nicholas R.", "orcid": "0000-0002-5203-3635", "clpid": "Hutzler-N-R" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Shaw", "given_name": "Matthew D.", "clpid": "Shaw-M-D" }, { "family_name": "Spiropulu", "given_name": "Maria", "orcid": "0000-0001-8172-7081", "clpid": "Spiropulu-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Superconducting Nanowire Single-Photon Detectors (SNSPDs) are high-performance photon counting detectors, typically operated just a few degrees above absolute zero. Comprising a current-biased nanowire transitioning between superconducting and resistive states upon photon absorption, SNSPDs generate voltage pulses for precise photon arrival time measurement. Initially demonstrated in the 1990s, SNSPDs are now mature devices widely employed in various fields, including space communication, biological imaging, and quantum technology. This\u00a0thesis\u00a0explores techniques to enhance usable count rate, dark count rate, timing resolution, and photon number resolution for both emerging and established SNSPD designs. We introduce a free space optical filtering method to minimize SNSPD dark count rates which is competitive with the state-of-the-art for fiber coupled SNSPDs, and especially impactful for space communication applications. We go on to study dynamics that limit SNSPD maximum count rates, presenting a calibration and in-situ correction procedure to significantly reduce jitter at high rates without additional hardware or offline processing. With an eye towards space communication applications beyond NASA's Deep Space Optical Communication (DSOC) project, we present a high-rate Pulse Position Modulation communication demo with SNSPDs. In the process we uncover a rich photon-number dependent response in these detectors and devise methods to properly leverage and manage it. Finally, we employ low-jitter SNSPDs in a high-rate entanglement distribution system, achieving high entanglement visibilities, and distillable entanglement rates. \u00a0As this work focuses on optimizing SNSPD usage and analysis rather than device physics or fabrication, it is broadly applicable to any users of this single photon detection technology.
", "doi": "10.7907/tneb-9z27", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16304", "collection": "thesis", "collection_id": "16304", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02262024-184235077", "primary_object_url": { "basename": "Thesis-Hamidreza Akbari.pdf", "content": "final", "filesize": 8843486, "license": "other", "mime_type": "application/pdf", "url": "/16304/1/Thesis-Hamidreza Akbari.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Characterization and Tuning of Quantum Emitters in Hexagonal Boron Nitride", "author": [ { "family_name": "Akbari", "given_name": "Hamidreza", "orcid": "0000-0002-6073-3885", "clpid": "Akbari-Hamidreza" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" }, { "family_name": "Schwab", "given_name": "Keith C.", "orcid": "0000-0001-8216-4815", "clpid": "Schwab-K-C" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Hexagonal boron nitride (h-BN) is a two-dimensional material hosting atomic defects that serve as single-photon emitters, attributed to its large bandgap. Its high stability at room temperature, substantial Debye-Waller factor, and integrability into 2D devices make h-BN a compelling choice for quantum applications involving single-photon emitters.
\r\n\r\nInitially, we investigate the properties of emitters in h-BN to comprehend the limitations of their spectral linewidth. This study includes examining the effects of the host crystal's growth method, the emitter's environment (the substrate), and temperature. As a result, we identify two primary broadening regimes: thermal broadening and spectral diffusion. Secondly, we address spectral diffusion, the predominant broadening mechanism at cryogenic temperatures, which depends on local electrical charges near the emitter. We propose a device structure comprising graphene - emitter h-BN - buffer h-BN - graphene, designed to apply a DC electric field and suppress spectral diffusion. This approach leads to a dramatic two orders of magnitude reduction in linewidth, achieving Fourier transform-limited linewidth.
\r\n\r\nMoreover, we explored the 3D dipole orientation and axial location of emitters within an h-BN crystal slab by coupling them to a phase change material. We discovered that the dipole orientation of some emitters is predominantly out-of-plane, and these emitters tend to exist close to the crystal's surfaces. This insight aids in the quest to determine the atomic structure of the emitters.
\r\n\r\nFinally, we examine the photon statistics of single-photon beams generated by h-BN emitters. We demonstrate that these beams exhibit sub-Poissonian statistics with both pulsed and continuous-wave excitation. Our findings reveal that excitation power can serve as a control to alter photon statistics, and we utilize this dependency to illustrate how photon statistics influence the use of quantum emitters in quantum random number generation applications.
", "doi": "10.7907/qz1v-3696", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16317", "collection": "thesis", "collection_id": "16317", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03062024-043923772", "primary_object_url": { "basename": "Zheng_Tianzhe_2024_final.pdf", "content": "final", "filesize": 20073003, "license": "other", "mime_type": "application/pdf", "url": "/16317/1/Zheng_Tianzhe_2024_final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Reconfigurable Metasurfaces in Nanoelectromechanical and Silicon-Organic Systems", "author": [ { "family_name": "Zheng", "given_name": "Tianzhe", "orcid": "0000-0001-7058-5196", "clpid": "Zheng-Tianzhe" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry", "orcid": "0000-0003-1783-1380", "clpid": "Vahaha-K" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Over the past decade, metasurfaces, a technology referring to 2D or 3D engineered nanostructures, has demonstrated itself as a groundbreaking solution for creating compact and multifunctional optical devices. Moreover, the integration of metasurfaces with various modulation techniques enables compact yet high-performance active optical systems. In this thesis I explore various optical modes in engineered nanostructures and apply different design techniques to improve the amplitude and phase response of free-space modulators.
\r\n\r\nIn Chapter 1 and 2, we first briefly introduce the concept of reconfigurable metasurfaces and its state of art. Then we introduce several nanophotonic concepts that will be used frequently in later projects and discuss the potential directions to improve modulator's performance.
\r\n\r\nIn Chapter 3, we find that the dual-mode resonant metasurfaces could improve the phase response in the nanoelectromechanical system(NEMS). The interaction between the quasi-bond state in the continuum and guided mode resonance boosts the phase response up to 144 degrees.
\r\n\r\nIn Chapter 4, the design target is to utilize the high-Q mode to decrease the driving voltage of the NEMS system to CMOS level. Motivated by the low-index confinement property of the slot mode, the device achieves over 10% reflection amplitude modulation with only 1.5V in the experiment. In addition, by adding a bottom gold mirror, 1.8\u03c0 phase response is numerically observed. Based on the success of this device, we propose a design that could achieve subwavelength wavefront control. As a example, we show a 3-pixel optical beam deflector with 75% diffraction efficiency.
\r\n\r\nIn Chapter 5, we extend the use of the slot mode into silicon-organic hybrid devices. The utilization of the slot mode achieves efficient electro-optic tuning under 17V in free space with a MHz modulation speed. We also explored various methods to enhance its phase response and discuss its feasibility. The spatial phase modulation design is also proposed with a 12-period supercell pixel. The beam deflector achieves 70% diffraction efficiency numerically.
\r\n\r\nIn Chapter 6, we bring this dissertation to a close and outline potential directions for future research.
\r\n\r\nThis thesis provides a foundation for the development of high-resolution and power-efficient one-dimensional spatial light modulators and showcases the potential of reconfigurable metasurfaces.
", "doi": "10.7907/2kmq-da15", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16434", "collection": "thesis", "collection_id": "16434", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05292024-213136069", "primary_object_url": { "basename": "shi-ning_sun_2024.pdf", "content": "final", "filesize": 8382143, "license": "other", "mime_type": "application/pdf", "url": "/16434/1/shi-ning_sun_2024.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Digital Quantum Simulation of Quantum Many-Body Systems", "author": [ { "family_name": "Sun", "given_name": "Shi-Ning", "orcid": "0000-0002-5984-780X", "clpid": "Sun-Shi-Ning" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Chan", "given_name": "Garnet K.", "orcid": "0000-0001-8009-6038", "clpid": "Chan-G-K" }, { "family_name": "Chen", "given_name": "Xie", "orcid": "0000-0003-2215-2497", "clpid": "Chen-Xie" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Quantum computing has emerged as a promising technology, heralding a new era of computational capabilities, with the simulation of quantum many-body systems as one of its primary objectives. Although fault-tolerant quantum computers are still years away, noisy intermediate-scale quantum (NISQ) devices have been fabricated and leveraged to perform small-scale quantum simulations. In this thesis, we demonstrate simulations of quantum many-body systems on these near-term quantum computers. We specifically focus on physical quantities pertaining to the linear-response framework, which include two-point correlation functions and Green's functions, of small-scale spin and molecular models. Additionally, as quantum hardware increases in qubit count, simulation of these quantum algorithms on classical computers that closely resemble those planned for execution on quantum hardware becomes increasingly critical. The final part of this thesis examines such a simulation using tensor network algorithms on classical computers.
\r\n\r\nWe first present the study of finite-temperature physics of spin models on quantum hardware. Employing the quantum imaginary time evolution (QITE) algorithm, we demonstrate the computation of diverse finite-temperature observables, including energy, static and dynamical correlation functions, and excitation spectra of the Heisenberg model and the transverse-field Ising model of up to four sites on five-qubit IBM Quantum devices. Accurate determination of these finite-temperature properties on quantum computers is made possible by several algorithmic improvements, including a method to exploit symmetries that reduces the quantum resources required by QITE, circuit optimization procedures to reduce circuit depth, and error-mitigation techniques to improve the quality of raw hardware data. This work demonstrates that the ansatz-independent QITE algorithm is capable of computing diverse finite-temperature observables on near-term quantum devices.
\r\n\r\nThe second work implements an algorithm for frequency-domain response properties of diatomic molecules using a novel high-fidelity three-qubit iToffoli gate. Although it is natural to compute response properties in the time domain due to the natural ability of quantum computers to apply unitary time evolutions, obtaining the frequency-domain properties from the time-domain properties typically requires a time duration that results in quantum circuits exceeding the circuit depth limitations of near-term quantum computers. In this work, we carry out computations of the response properties directly in the frequency domain using the linear combination of unitaries (LCU) algorithm. Execution of the LCU-based protocol on quantum hardware is enabled by the iToffoli gate, which enables a ~50\\% reduction in circuit depth and ~40\\% reduction in circuit execution time in the LCU circuits compared to the traditional gate set. We show that the molecular properties obtained with the iToffoli gate exhibit comparable or better agreement with analytical results than those obtained when CZ gates are the only multi-qubit gates. This work is among the first demonstrations of the practical usage of a native multi-qubit gate in quantum simulation, with diverse potential applications to near-term quantum computation.
\r\n\r\nFinally, this thesis conducts a tensor network simulation of measurement-induced state preparation on classical computers. Specifically, we simulate the phase transition in random-bond Ising models (RBIM) by performing measurements on the cluster states. The simulation is carried out on NVIDIA H100 graphical processing units (GPUs) using the cuQuantum library. We present simulation of correlation functions in one dimension (1D) and ferromagnetic susceptibilities in two dimensions (2D), observing a phase transition from the ferromagnetic phase to spin-glass phase in the 2D model. The tensor network simulation incorporates up to 176 qubits on the 2D lattice. This work paves the way for future explorations of tensor network simulations of measurement-induced quantum computation protocols with GPU-accelerated tensor network libraries.
", "doi": "10.7907/xm9j-9x23", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:15117", "collection": "thesis", "collection_id": "15117", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03112023-174134421", "primary_object_url": { "basename": "XueyueZhang_PhDThesis.pdf", "content": "final", "filesize": 26342007, "license": "other", "mime_type": "application/pdf", "url": "/15117/1/XueyueZhang_PhDThesis.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Superconducting Circuit Architectures Based on Waveguide Quantum Electrodynamics", "author": [ { "family_name": "Zhang", "given_name": "Xueyue", "orcid": "0000-0001-8994-0629", "clpid": "Xueyue-Sherry-Zhang" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Quantum science and technology provides new possibilities in processing information, simulating novel materials, and answering fundamental questions beyond the reach of classical methods. Realizing these goals relies on the advancement of physical platforms, among which superconducting circuits have been one of the leading candidates offering complete control and read-out over individual qubits and the potential to scale up. However, most circuit-based multi-qubit architectures only include nearest-neighbor (NN) coupling between qubits, which limits the efficient implementation of low-overhead quantum error correction and access to a wide range of physical models using analog quantum simulation.
\r\n\r\nThis challenge can be overcome by introducing non-local degrees of freedom. For example, photons in a shared channel between qubits can mediate long-range qubit-qubit coupling arising from light-matter interaction. In addition, constructing a scalable architecture requires this channel to be intrinsically extensible, in which case a one-dimensional waveguide is an ideal structure providing the extensible direction as well as strong light-matter interaction.
\r\n\r\nIn this thesis, we explore superconducting circuit architectures based on light-matter interactions in waveguide quantum electrodynamics (QED) systems. These architectures in return allow us to study light-matter interaction, demonstrating strong coupling in the open environment of a waveguide by employing sub-radiant states resulting from collective effects. We further engineer the waveguide dispersion to enter the topological photonics regime, exploring interactions between qubits that are mediated by photons with topological properties. Finally, towards the goals of quantum information processing and simulation, we settle into a multi-qubit architecture where the photon-mediated interaction between qubits exhibits tunable range and strength. We use this multi-qubit architecture to construct a lattice with tunable connectivity for strongly interacting microwave photons, synthesizing a quantum many-body model to explore chaotic dynamics. The architectures in this thesis introduce scalable beyond-NN coupling between superconducting qubits, opening the door to the exploration of many-body physics with long-range coupling and efficient implementation of quantum information processing protocols.
", "doi": "10.7907/c7d8-nn87", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15155", "collection": "thesis", "collection_id": "15155", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05072023-204014466", "primary_object_url": { "basename": "Adrian_Thesis.pdf", "content": "final", "filesize": 5483304, "license": "other", "mime_type": "application/pdf", "url": "/15155/3/Adrian_Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Digital Quantum Simulation of Physical Systems on Noisy Intermediate-Scale Quantum Computers", "author": [ { "family_name": "Tan Teck Keng", "given_name": "Adrian", "orcid": "0000-0002-6660-0397", "clpid": "Tan-Teck-Keng-Adrian" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Chan", "given_name": "Garnet K.", "orcid": "0000-0001-8009-6038", "clpid": "Chan-G-K" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Current quantum computers are characterized as having the order of 5-100 qubits, with limited connectivity restricting two-qubit operations to nearest neighbors, and with too much noise to achieve fault-tolerance. Such devices, called noisy intermediate-scale quantum (NISQ) devices, have been demonstrated to have sufficient coherent lifetime to perform interesting experiments motivated by quantum information sciences. This motivates the question of whether such devices can be utilized to study physical systems commonly encountered in condensed matter and quantum chemistry.
\r\n\r\nIn this thesis, we address the open problem of identifying approaches to perform quantum simulations of physical systems on NISQ devices. We begin our study by considering the Hamiltonian ground state problem, a task routinely solved in numerical studies of materials and molecules. We provided a new quantum primitive, the quantum imaginary time evolution (QITE), that provides a practical approach to solve the Hamiltonian ground state problem. In addition, the QITE subroutine can be used in a Lanczos scheme to speed up convergence time.
\r\n \r\nNext, we consider the problem of performing finite temperature simulations and demonstrate how QITE can be used as a subroutine to develop scalable and feasible approaches to perform such calculations on a quantum computer. More specifically, we develop routines to obtain thermal averages by sampling minimally entangled thermal states, and also free energy by evaluating the partition function directly.
\r\n \r\nIn our final study, we consider the study of topological states of matter, which do not fit within the Landau paradigm of local order parameters associated with symmetry breaking, and have been shown to exhibit unusual behavior. We show how a specific class of topological states of matter, the symmetry-protected topological states can be feasibly realized on present NISQ devices and their unusual behavior experimentally validated. Our study provides a benchmark of capabilities of state-of-the-art NISQ devices to study these interesting phases of matter.
", "doi": "10.7907/wget-ws64", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15151", "collection": "thesis", "collection_id": "15151", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05052023-033943351", "type": "thesis", "title": "Mock Observations of the Sunyaev-Zel\u2019dovich Effect in Massive Galaxy Clusters and a Six-Layer Integral Antireflective Structure for Silicon Optics", "author": [ { "family_name": "Macioce", "given_name": "Theodore Kenneth", "orcid": "0000-0002-3156-6627", "clpid": "Macioce-Theodore-Kenneth" } ], "thesis_advisor": [ { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "thesis_committee": [ { "family_name": "Zmuidzinas", "given_name": "Jonas", "orcid": "0000-0002-3330-5439", "clpid": "Zmuidzinas-J" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" }, { "family_name": "Hopkins", "given_name": "Philip F.", "orcid": "0000-0003-3729-1684", "clpid": "Hopkins-P-F" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Part 1: Measuring the kinematic Sunyaev-Zel\u2019dovich (kSZ) effect is a promising observational tool to constrain both cosmic growth and galaxy cluster formation. As millimeter-wave telescopes gain sensitivity and angular resolution over multiple frequency bands, high signal-to-noise imaging of the kSZ effect in large samples of galaxy clusters will become increasingly feasible. However, maximizing the science reach of these upcoming data will require more sophisticated analysis methods to characterize and remove contamination from a range of unwanted signals, such as the emission from dusty star forming galaxies. Current predictions of kSZ-derived constraints do not account for these effects in sufficient detail. Moreover, they typically rely on Fisher matrix analyses, which cannot fully capture the degeneracies among the physical parameters describing the cluster. We present a mock observation and analysis pipeline to determine the science reach of kSZ galaxy cluster observations that employs more detailed noise models and more sophisticated analysis methods. From our mock observations, we derive new forecasts of the constraining power of next-generation telescopes on cluster peculiar velocities for several instrument configurations from the 10-m, 30-m, and 50-m classes. These forecasts will inform the designs of next-generation telescopes targeting kSZ observations and will indicate the optimal instrumentation for both cosmological and cluster-scale constraints. The software pipeline we develop will also be directly usable as an analysis tool once observations from such telescopes become available.
\r\n\r\nPart 2: Silicon optics can greatly benefit future millimeter and submillimeter astronomical instruments thanks to silicon\u2019s useful properties such as low loss, high refractive index, and high strength. However, silicon\u2019s high index (n = 3.4) necessitates antireflection (AR) treatment, which has proven a major challenge, especially for the multilayer treatments required for wide spectral bandwidths. We present our approach to this challenge, in which we develop a wide-bandwidth integral AR structure for silicon optics that uses a novel fabrication technique that combines deep reactive ion etching (DRIE) and wafer bonding. We have previously demonstrated a two-layer AR structure for windows over a 1.6:1 bandwidth and are currently fabricating a four-layer coating for a 4:1 bandwidth. Here, we focus on a design for a six-layer structure optimized to give -20 dB reflection between 80 and 420 GHz (5.25:1 bandwidth), which will be useful for future multicolor SZ observations.
", "doi": "10.7907/w1ds-j507", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15205", "collection": "thesis", "collection_id": "15205", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05242023-033922764", "primary_object_url": { "basename": "Luis_Ledezma_thesis_2023.pdf", "content": "final", "filesize": 19438472, "license": "other", "mime_type": "application/pdf", "url": "/15205/1/Luis_Ledezma_thesis_2023.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Towards Universal Integrated Laser Sources with Nonlinear Photonics", "author": [ { "family_name": "Ledezma", "given_name": "Luis M.", "orcid": "0000-0002-0365-1672", "clpid": "Ledezma-Luis-M" } ], "thesis_advisor": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Lasers are ubiquitous in modern technology with different applications typically requiring different laser wavelengths. However, a given laser can operate only in a relatively narrow spectral region given by the particular material used to build the laser. This leads to using several lasers when several wavelengths are required. Nonlinear photonic devices pose a solution to this problem by transferring energy from single lasers to vast regions of the electromagnetic spectrum. But, despite more than 60 years of development in nonlinear photonics, most nonlinear devices remain large, expensive, and confined to research laboratories.
\r\n\r\nIn this dissertation, we demonstrate a new generation of integrated nonlinear photonic devices based on the quadratic \u03c7(2) nonlinearity. Using the up-and-coming thin-film lithium niobate platform, we demonstrate ultrafast optical parametric amplifiers, parametric generation of ultrashort mid-infrared pulses, long pulses and frequency combs tunable over an octave bandwidth, and the first \u03c7(2) CW parametric oscillator directly pumped by a single commercial diode laser. These results represent key milestones towards compact and inexpensive universal laser sources.
", "doi": "10.7907/ag5t-r511", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15127", "collection": "thesis", "collection_id": "15127", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04032023-062047194", "primary_object_url": { "basename": "SouvikBiswas_Thesis_Final.pdf", "content": "final", "filesize": 15418859, "license": "other", "mime_type": "application/pdf", "url": "/15127/1/SouvikBiswas_Thesis_Final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Electro-Optic Excitations in van der Waals Materials for Active Nanophotonics", "author": [ { "family_name": "Biswas", "given_name": "Souvik", "orcid": "0000-0002-8021-7271", "clpid": "Biswas-Souvik" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Nadj-Perge", "given_name": "Stevan", "orcid": "0000-0002-2394-9070", "clpid": "Nadj-Perge-S" }, { "family_name": "Hsieh", "given_name": "David", "orcid": "0000-0002-0812-955X", "clpid": "Hsieh-David" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "da Jornada", "given_name": "Felipe H.", "orcid": "0000-0001-6712-7151", "clpid": "da-Jornada-FElipe-H" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "van der Waals materials are emerging due to their unique properties such as atomic thickness, diverse quasiparticle optical resonances, and no requirement for lattice matching. While there is a vast variety of materials, semiconductors hold a special place for opto-electronic and linear/non-linear optical studies. Black phosphorus (BP), a 2D quantum-well with direct bandgap and puckered crystal structure, is a compelling platform for this research direction. In this thesis, we investigate fundamental optical excitations in novel low-dimensional quantum materials to achieve strong light-matter interaction and integrate with nanophotonic motifs for low-footprint, reconfigurable optical technology, focusing primarily on black phosphorus and transition metal dichalcogenides.
\r\n\r\nThe thesis begins with the 'thin film limit' of van der Waals materials, between 5 and 20 nm thickness range. Chapters 2 and 3 explore how few-layer black phosphorus hosts interband and intraband optical excitations that can be strongly modified with gate-controlled doping and electric field, displaying epsilon near zero and hyperbolic behavior in the mid and far-infrared. In atomic thickness, strongly bound excitonic quasiparticles dominate the optical response. In Chapter 4, we investigate electrically tunable excitons in tri-layer black phosphorus, demonstrating a reconfigurable birefringent material that, when coupled with a Fabry-Perot cavity, enables the realization of a versatile and broadband polarization modulator. In Chapter 5, we examine the ultimate limit of a monolayer, studying MoTe2 via photoluminescence measurements and first-principles GW+BSE calculations, highlighting the Rydberg series associated with the exciton and its gate-tunability to understand strong electron-exciton interactions. In Chapter 6, we show how such excitons in monolayer black phosphorus can be strongly quantum confined at natural edges of exfoliated flakes, leading to highly temporally coherent emission. This emission is gate-tunable and understood via transmission electron microscopy and first-principles GW+BSE calculations of phosphorene nanoribbons to be originating from atomic reconstructions of the edge coupled with strain and screening effects.
\r\n\r\nOverall, our work highlights the potential of van der Waals materials for various electro-optical excitations and their applications in active nanophotonics.\r\n
", "doi": "10.7907/tz4z-ed06", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15119", "collection": "thesis", "collection_id": "15119", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03142023-213121023", "type": "thesis", "title": "Parametrically-Driven Nonlinear Optical Resonators and their Networks for Sensing and Computing", "author": [ { "family_name": "Roy", "given_name": "Arkadev", "orcid": "0000-0001-5659-8388", "clpid": "Roy-Arkadev" } ], "thesis_advisor": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "New physics and novel applications in various fields ranging from biology, and spectroscopy, to manipulation of quantum systems are driven by the availability of coherent light sources including frequency combs in the visible and mid-infrared spectral regimes. Nonlinear optical systems, that are parametrically driven by technologically mature near-infrared lasers, are leveraged in this regard to access challenging wavelengths where conventional lasers may be unavailable. It is of paramount importance to miniaturize these systems and replace the traditional bulky setups thereby paving the way for a plethora of applications. Optical parametric oscillators are among the most prominent examples of such nonlinear systems and beyond their indispensable usage as light sources (both classical and quantum) their unique non-equilibrium dynamics can endow a wealth of functionalities absent in their linear counterparts. These properties can be engineered and utilized for realizing highly sensitive sensors as well as special-purpose computing hardware that may outperform conventional digital computers. A network of these coupled parametric oscillators can be made to interact leading to emergent behaviors that are not expected from the individual constituents.
\r\n\r\nIn this work, we experimentally and theoretically study the dynamics of individual and coupled optical parametric oscillators towards sensing and computing applications. We explore a previously avoided regime of operation for generating ultra-short pulses from these parametrically driven nonlinear resonators that lead to extreme pulse compression. We engineer the nonlinear dynamics of these systems to realize all-optical spectral phase transitions (both first-order and second-order) that behave as highly-sensitive sensors. We show how these critical phenomena can be utilized to enhance the solution accuracy of physics-based solvers in finding optimum solutions to combinatorial optimization problems in the context of coherent Ising machines. We also realize optical parametric oscillators in integrated lithium-niobate nanophotonic platform and demonstrate a mid-infrared frequency comb source that is widely tunable over an octave accompanied by visible frequency comb generation. We develop a comprehensive description to investigate the noise properties of optical parametric oscillators that provide new insights into the phase noise behavior of optical parametric oscillators in their various operating regimes. Finally, we propose a system of parametrically driven resonators as a synthetic medium with highly reconfigurable interactions that can host a plethora of emergent phenomena ranging from topological behaviors to non-Hermitian dynamics. These networks of nonlinear resonators display intriguing dynamical properties in contrast to their static counterparts in condensed-matter physics with implications in quantum sensing and robust device functionality.
", "doi": "10.7907/xsyc-6668", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:14579", "collection": "thesis", "collection_id": "14579", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05152022-181826611", "type": "thesis", "title": "Microwave-to-Optical Transduction Using Rare-Earth Ions", "author": [ { "family_name": "Rochman", "given_name": "Jake Herschel Lebi", "orcid": "0000-0002-8475-3389", "clpid": "Rochman-Jake-Herschel-Lebi" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" }, { "family_name": "Schwab", "given_name": "Keith C.", "orcid": "0000-0001-8216-4815", "clpid": "Schwab-K-C" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_eng" } ], "abstract": "Superconducting qubits that operate at microwave frequencies are one of the most promising platforms for quantum information processing. However, connecting distant processors with microwave photons is challenging since microwave photons suffer from thermal noise and large propagation losses in room temperature components.
\r\n\r\nConversely, optical photons within the telecommunications band are known to have extremely low loss in optical fiber and the thermal noise is minuscule at room temperature. In order to interface superconducting qubits with room temperature optical photons, a quantum transducer is required that can convert photons between microwave and optical frequencies.
\r\n\r\nThis thesis describes the development of a microwave-to-optical transducer using an ensemble of erbium ions, doped within a yttrium orthovanadate crystal, that are simultaneously coupled to a superconducting microwave resonator and a photonic crystal optical resonator. The erbium ions have spin transitions that couple to the microwave resonator and optical transitions at telecom wavelengths that couple to the optical resonator.
", "doi": "10.7907/4h2f-wj87", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14286", "collection": "thesis", "collection_id": "14286", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06232021-050358035", "type": "thesis", "title": "Light Modulation with Vanadium Dioxide-Based Optical Devices", "author": [ { "family_name": "Kim", "given_name": "Yonghwi", "orcid": "0000-0002-6652-7994", "clpid": "Kim-Yonghwi" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "This thesis focuses on active material-based tunable optical devices. In particular, I have been working on tunable optical devices based on vanadium dioxide (VO2), which can produce tunable optical responses, such as amplitude, phase, thermal emission, and quantum emission. The modulations of light are achieved by coupling the phase-transition material with the precisely designed resonant structures or by placing it close to quantum emitters. This thesis presents three research streams, which aim at experimentally demonstrating the dynamically tunable optical responses using VO2. First, we propose and experimentally demonstrate an electrically tunable VO2-based reflectarray metasurface that exhibits largely tunable optical responses in the near-infrared region. We incorporate VO2 directly into the plasmonic resonator, which undergoes a phase transition triggered by Joule heating. The induced plasmonic resonance modulation is accompanied by a large and continuous modulation in optical responses, such as amplitude, resonance wavelength, and phase. Second, we propose and demonstrate an active tuning of thermal emission from VO2-based metasurfaces. We introduce a thin VO2 film as an absorbing layer on top of a metal reflector. This layer is coupled with a dielectric resonator, with a dielectric spacer placed between them. Upon undergoing a phase transition triggered by heating, the induced absorption tuning of the VO2 layer is accompanied by modulation in the absorption spectra of the coupled structure. We experimentally show narrowband absorption spectra, which can be tuned by controlling the VO2 temperature. Finally, we experimentally demonstrate the axial position of quantum emitters in a multilayered hexagonal boron nitride (hBN) flake with nanoscale accuracy, which is enabled through the modification of a photonic density of states by introducing VO2. Furthermore, we observe a sharp distance-dependent photoluminescence response by modulating the optical environment of an emitter placed close to the hBN/VO2 interface.
", "doi": "10.7907/pkxj-9584", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14344", "collection": "thesis", "collection_id": "14344", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08272021-165922711", "type": "thesis", "title": "Multifunctional Volumetric Metaoptics", "author": [ { "family_name": "Ballew", "given_name": "Conner Kiley", "orcid": "0000-0003-4854-8342", "clpid": "Ballew-Conner-Kiley" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Bouman", "given_name": "Katherine L.", "orcid": "0000-0003-0077-4367", "clpid": "Bouman-K-L" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Golwala", "given_name": "Sunil", "orcid": "0000-0002-1098-7174", "clpid": "Golwala-S-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical systems are often comprised of modular arrangements of components, and the improvement of these systems has historically leaned on the precise manufacturing and alignment of the comprising elements. This provides an intuitive pathway to optical design, but ultimately yields systems that are far bulkier than required by the laws of physics. It is often the case that the required degrees of freedom to achieve complex tasks is present within dielectric volumes that are only several wavelengths per side, and these degrees of freedom can be accessed by patterning the dielectric volume with subwavelength resolution. Even in such small volumes, all of the fundamental properties of light (wavelength, polarization, k-vector) can be controlled which opens the possibility for extremely multifunctional, compact image sensor elements. The determination of the refractive index distribution of these devices has historically been a challenging inverse-design problem, and the fabrication of 3D dielectric devices is a challenge unique to different regimes of the electromagnetic spectrum. This thesis utilizes current state-of-the-art optimization techniques to design multifunctional volumetric devices, and theoretically expands upon the techniques to facilitate the optimization of high index contrast structures. Multiple microwave prototypes are measured, devices operating at terahertz frequencies are fabricated using silicon micromachining, and optical devices with resolutions achievable with CMOS processing techniques are studied for next-generation camera sensors.
", "doi": "10.7907/dn7h-6r72", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14371", "collection": "thesis", "collection_id": "14371", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09242021-181127485", "type": "thesis", "title": "High Sensitivity Time-Varying Systems In Photonics and Electronics", "author": [ { "family_name": "Porsandeh Khial", "given_name": "Parham", "orcid": "0000-0002-3242-8541", "clpid": "Porsandeh-Khial-Parham" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Integrated electronics and photonics have been revolutionizing our daily lives for decades. However, the demand for high-speed communications, low-latency networks, and high-performance optical and electrical sensors continues to grow. In order to keep up with this demand as well as be able to address upcoming and unknown challenges, we need to explore unconventional solutions. Moving away from existing systems and traditional architectures allows us to take a deeper look at these challenges and potentially come up with nontrivial answers. In this thesis, unconventional approaches to implementing high-performance optical and electrical sensors and systems are investigated. Among these unorthodox solutions are time-varying architectures which led to completely new devices, sensors with dramatically improved sensitivity, and the breaking of known trade-offs.
\r\n\r\nBy developing a time-varying method that we call reciprocal sensitivity enhancement, we demonstrated a nanophotonic optical gyroscope (NOG) for the first time. The efficacy of this method is borne out by its ability to improve the performance of optical gyroscopes by two orders of magnitude. This sensitivity-enhancement method filters out reciprocal imperfections and noise, thereby increasing the overall signal-to-noise ratio. Next, the same approach is used to boost the performance of resonance-based magnetic biosensors. By merging two biosensors and taking advantage of the frequency response of magnetic beads, time-division switching cancels out most of the correlated noise. This solution pushes the sensitivity of this sensor below parts-per-million (PPM) levels for long periods of time \u2014 a property which is desirable in many biosensing applications.
\r\n\r\nAdditionally, an electrical scalable router that mitigates line-of-sight issues in next-generation wireless systems is introduced. This novel design does not require any shared timing reference to form a coherent array and uses a time-varying baseband to create a proper true-time delay. Next, we discuss how radiating elements in silicon-photonics platforms can be engineered to create a passive lensless camera. By applying a robust reconstruction algorithm, the captured image can be faithfully recovered. The same concept can be used in multi-mode nanophotonic antennas to alleviate the field-of-view (FOV)-aperture trade-off.
\r\n\r\nFinally, a hybrid photonic transmitter/receiver architecture, an electrical full-duplex transceiver with one nonreciprocal element, and a nested-ring optical modulator are presented.
", "doi": "10.7907/qzj9-rz93", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14655", "collection": "thesis", "collection_id": "14655", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312022-105606161", "primary_object_url": { "basename": "Vinicius_Ferreira_Thesis.pdf", "content": "final", "filesize": 26970280, "license": "other", "mime_type": "application/pdf", "url": "/14655/1/Vinicius_Ferreira_Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Waveguide Quantum Electrodynamics with Superconducting Slow-Light Waveguide Circuits", "author": [ { "family_name": "Ferreira", "given_name": "Vinicius Thaddeu dos Santos", "orcid": "0000-0002-9522-2567", "clpid": "Ferreira-Vinicius-Thaddeu-dos-Santos" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Brandao", "given_name": "Fernando", "orcid": "0000-0003-3866-9378", "clpid": "Brand\u00e3o-F-G-S-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Waveguide quantum electrodynamics (QED) refers to the study of quantum emitters (qubits) coupled to a single mode waveguide - a 1D electromagnetic reservoir with a continuum of states. This paradigmatic quantum-optical system can serve as a test-bed for experimental investigations in many-body physics, quantum non-linear optics, reservoir engineering, non-Markovian physics, quantum networks, and quantum computing. While such a system can be realized in a variety of physical platforms, superconducting quantum circuits are well suited to the study of waveguide QED due their readily available strong light-matter interaction strengths.
\r\n\r\nOf particular interest is the ability to tailor the dispersion relation and modal properties of the waveguide beyond that of a conventional waveguide with linear dispersion. For example, through periodic modulation of the geometry of a waveguide, or through the fabrication of an array of coupled resonant elements, novel electromagnetic responses can be engineered. These include spectral constriction of the 1D continuum to a transmission band of finite bandwidth, enhanced or suppressed emission rates of quantum emitters into the waveguide that are dependent on their frequencies, and extreme slowing of the velocity of light. Such attributes of dispersive waveguides can be leveraged to substantially enrich the physics and applications of qubit-waveguide systems.
\r\n\r\nIn this thesis, we demonstrate the design, fabrication, and characterization of a slow-light waveguide (SLWG) comprised of an array of coupled lumped-element superconducting microwave resonators, and present on various experiments involving superconducting transmon qubits coupled to the SLWG. We investigate the physics of a qubit strongly coupled to the SLWG reservoir by tuning its frequency across the passband of this waveguide, where we find substantial changes to the qubit emission rate, along with oscillatory energy relaxation of the qubit resulting from the beating of bound and radiative dressed qubit-photon states. Further, upon addition of a reflective boundary to one end of the waveguide, we observe revivals in the qubit population on a timescale 30 times longer than the inverse of the qubit's emission rate, corresponding to the round-trip travel time of an emitted photon.
\r\n\r\nIn addition, we show how we leveraged the ability to induce this non-Markovian time-delayed feedback via the SLWG's long delay to generate multidimensional cluster states of itinerant microwave photonic qubits. By utilizing the SLWG as a delay line with 240 ns round-trip delay, a single flux-tunable transmon qubit as a quantum emitter, and a second auxiliary transmon as a switchable mirror, we achieve rapid, shaped emission of entangled photon wavepackets, and effect time-delayed feedback within the waveguide between previously emitted photons and the emitter qubit. We leverage these capabilities to generate a 2D cluster state of four photons with 70% fidelity, as verified by tomographic reconstruction of the quantum state. We conclude by discussing directly realizable novel follow-up experiments that involve a continuously driven qubit in the presence of time-delayed feedback, and discuss how our cluster-state generation scheme could be straightforwardly extended to generation of even larger multidimensional cluster states, thereby enabling utilization of such states for quantum information processing techniques in the microwave domain.
", "doi": "10.7907/y4vk-a827", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14484", "collection": "thesis", "collection_id": "14484", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01222022-151042739", "primary_object_url": { "basename": "Thesis_JashBanker_final.pdf", "content": "final", "filesize": 63180342, "license": "other", "mime_type": "application/pdf", "url": "/14484/1/Thesis_JashBanker_final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Photonic and Phononic Band Gap Engineering for Circuit Quantum Electrodynamics and Quantum Transduction", "author": [ { "family_name": "Banker", "given_name": "Jash Haren", "orcid": "0000-0002-2130-0825", "clpid": "Banker-Jash-Haren" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The ability to pattern materials at the wavelength and sub-wavelength scale has led to the concept of photonic crystals and metamaterials - artificially engineered structures that exhibit electromagnetic properties not found in conventional materials. Such engineered structures offer the ability to slow down and even inhibit the propagation of electromagnetic waves giving rise to a photonic band gap and a sharply varying photonic density of states.
\r\n\r\nQuantum emitters in the presence of an electromagnetic reservoir with varying density of states can undergo a rich set of dynamical behavior. In particular, the reservoir can be tailored to have a memory of past interactions with emitters, in contrast to memory-less Markovian dynamics of typical open systems. In part 1 of this thesis, we investigate the non-Markovian dynamics of a superconducting qubit strongly coupled to a superconducting metamaterial waveguide engineered to have both a sharp spectral variation in its transmission properties and a slowing of light by a factor of 650. Tuning the qubit into the spectral vicinity of the passband of this slow-light waveguide reservoir, we observe a 400-fold change in the emission rate of the qubit, along with oscillatory energy relaxation of the qubit resulting from the beating of bound and radiative dressed qubit-photon states. Further, upon addition of a reflective boundary to one end of the waveguide, we observe revivals in the qubit population on a timescale 30 times longer than the inverse of the qubit\u2019s emission rate, corresponding to the round-trip travel time of an emitted photon. With this superconducting circuit platform, future studies of multi-qubit interactions via highly structured reservoirs and the generation of multi-photon highly entangled states are possible.
\r\n\r\nWhile microwave frequency superconducting circuits are near ideal testbeds for quantum electrodynamics experiments of the type discussed in part 1, microwave photons are not well suited for transmission of quantum information over long distances due to the presence of a large thermal background at room temperature. Optical photons are ideal for quantum communication applications due to their low propagation loss at room temperature. Coherent transduction of single photons from the microwave to the optical domain has the potential to play a key role in quantum networking and distributed quantum computing. In part 2 of this thesis, we extend the notion of band gap engineering to the optical and acoustic domain and present the design of a piezo-optomechanical quantum transducer where transduction is mediated by a strongly hybridized acoustic mode of a lithium niobate piezoacoustic cavity attached to a silicon optomechanical crystal patterned on a silicon-on-insulator substrate. We estimate an intrinsic transduction efficiency of 29% with <0.5 added noise quanta when our transducer is resonantly coupled to a superconducting transmon qubit and operated in pulsed mode. Our design involves on-chip integration of a superconducting qubit with the piezo-optomechanical transducer. Absorption of stray photons from the optical pump used in the transduction process is known to cause excess decoherence and noise in the superconducting circuit. The recovery time of the superconducting circuit after the optical pulse sets a limit on the transducer repetition rate. We fabricate niobium based superconducting circuits on a silicon substrate and test their response to illumination by a 1550 nm laser. We find a recovery time of ~ 10 \u03bcs, indicating that a repetition rate of 10 kHz should be possible. Combined with the expected efficiency and noise metrics of our design, we expect that a transducer in this parameter regime would be suitable to realize probabilistic schemes for remote entanglement of superconducting quantum processors. We conclude by discussing some of the challenges associated with fabricating niobium superconducting qubits and lithium niobate piezoacoustic devices on silicon-on-insulator substrates and provide initial steps towards realizing our transducer design in the lab.
", "doi": "10.7907/jrf3-gx27", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14495", "collection": "thesis", "collection_id": "14495", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02122022-205429202", "primary_object_url": { "basename": "PhDthesis_EunjongKim_rev1.pdf", "content": "final", "filesize": 35817420, "license": "other", "mime_type": "application/pdf", "url": "/14495/1/PhDthesis_EunjongKim_rev1.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Waveguide Quantum Electrodynamics in Superconducting Circuits", "author": [ { "family_name": "Kim", "given_name": "Eun Jong", "orcid": "0000-0003-4879-8819", "clpid": "Kim-Eun-Jong" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Brandao", "given_name": "Fernando", "orcid": "0000-0003-3866-9378", "clpid": "Brand\u00e3o-F-G-S-L" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Preskill", "given_name": "John P.", "orcid": "0000-0002-2421-4762", "clpid": "Preskill-J" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Achieving an efficient interface of light and matter has been a principal goal in the field of quantum optics. A burgeoning paradigm in the study of light-matter interface is waveguide quantum electrodynamics (QED), where quantum emitters are coupled to a common one-dimensional waveguide channel. In this scenario, cooperative effects among quantum emitters emerge as a result of real and virtual exchange of photons, giving rise to new ways of controlling matter.
\r\n\r\nSuperconducting quantum circuits offer an exciting platform to study quantum optics in the microwave domain with artificial quantum emitters interfaced to engineered photonic structures on chip. Beyond revisiting the experiments performed in atom-based platforms, superconducting circuits enable exploration of novel regimes in quantum optics that are otherwise prohibitively challenging to achieve. Moreover, the unprecedented level of control over individual quantum degrees of freedom and good scalability of the system provided by state-of-the-art circuit QED toolbox set a promising direction towards the study of quantum many-body phenomena.
\r\n\r\nIn this thesis, I discuss waveguide QED experiments performed in superconducting quantum circuits where transmon qubits are coupled to engineered microwave waveguides. Employing the high flexibility and controllability of superconducting quantum circuits, we realize and explore various schemes for generating waveguide-mediated interactions between superconducting qubits. We also demonstrate an intermediate-scale quantum processor based on a dispersive waveguide QED system involving ten superconducting qubits, exploring quantum many-body dynamics in a highly controllable fashion. The work described in the thesis marks an important step towards the construction of scalable architectures for quantum simulation of many-body models and realization of efficient coupling schemes for quantum computation.
", "doi": "10.7907/bscv-b073", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14194", "collection": "thesis", "collection_id": "14194", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282021-193431717", "type": "thesis", "title": "Kerr Solitons and Brillouin Lasers in Optical Microresonators", "author": [ { "family_name": "Wang", "given_name": "Heming", "orcid": "0000-0003-3861-0624", "clpid": "Wang-Heming" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical resonators are capable of storing electromagnetic energies in the visible and infrared band. The light intensity is greatly enhanced within the resonator, which makes them suitable as a platform for nonlinear optics studies. Here, using silica microresonators as platforms, we explore the fundamental nonlinear dynamics of light induced by Kerr nonlinearity and Brillouin scattering. The first half of the thesis analyzes optical solitons as a result of Kerr nonlinearity, including its universal scaling, its dynamics in the presence of laser feedback, the analytical properties of its relativistic counterpart, as well as its applications as a wavelength reference. The second half of the thesis focuses on stimulated Brillouin lasers and their linewidth performance, demonstrating new performance levels of the Brillouin laser and two correction factors to its linewidth that have been established for semiconductor lasers.
", "doi": "10.7907/g1kf-5t57", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14086", "collection": "thesis", "collection_id": "14086", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02222021-054057067", "primary_object_url": { "basename": "Hybrid Si III-V Lasers for Next-generation Coherent Optical Communication.pdf", "content": "final", "filesize": 4976526, "license": "other", "mime_type": "application/pdf", "url": "/14086/1/Hybrid Si III-V Lasers for Next-generation Coherent Optical Communication.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Hybrid Si/III-V Lasers for Next-generation Coherent Optical Communication", "author": [ { "family_name": "Zhang", "given_name": "Zhewei", "orcid": "0000-0002-1211-7957", "clpid": "Zhang-Zhewei" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The most important application of semiconductor lasers is, without doubt, optical communication, the backbone of the information age. In the past few decades, incoherent optical communication with conventional semiconductor lasers, the III-V distributed feedback (DFB) lasers, has successfully fulfilled the global demand for the data rate. However, in order to support the rapidly growing Internet traffic of the 21st century, the transition from incoherent to coherent optical communication is inevitable, requiring new types of lasers, as the conventional III-V DFB lasers lack the phase coherence needed to serve as the light sources in coherent optical communication. The existent alternatives with high phase coherence are external cavity lasers (ECLs) and fiber lasers, whose high price and bulky size effectively thwart the upgrade of the current communication networks. This is the main motivation for us to develop high-coherence semiconductor lasers.
\r\n\r\nTo achieve the goal, we shall rethink and redesign semiconductor lasers. Advanced modern fabrication technology helps us to turn bold ideas into reality. Not only do we build semiconductor lasers on hybrid platforms, but also engineer elaborately the optical mode to enhance the lasers\u2019 phase coherence. The newly developed semiconductor lasers, hybrid Si/III-V lasers, are the core of the entire thesis. Their design principles, fabrication process, properties and performance in the coherent optical communication system will be presented and discussed. The experimental results show the Si/III-V lasers' superiority to their conventional counterparts.
\r\n\r\nAside from possessing high phase coherence, the Si/III-V lasers have great potential to be the light sources on the integrated photonic platforms. The fundamental obstacle thwarting photonic integration is optical feedback, to which the conventional semiconductor lasers are very sensitive. Without the protection provided by optical isolators, which unfortunately cannot be fabricated on chip, the performance of the conventional III-V DFB lasers could get significantly degraded by optical feedback. The Si/III-V lasers, with their built-in high-Q resonators, are very robust against optical feedback and can function properly in the isolator-free coherent optical communication systems. Thus, the cost of future optical networks can be further reduced by monolithically integrating passive photonic devices such as modulators and demodulators with the Si/III-V lasers.
\r\n\r\nFinally, all the studies centered on laser coherence trigger us to think deeply about the underlying relation between different means of characterizing laser coherence. A rigorous mathematical relation, the Central Relation, has been derived here, which not only unveils the fundamental relation between laser lineshape and frequency noise power spectral density (PSD) but also provides new methods of frequency noise controlling like optical filtering.
", "doi": "10.7907/y85t-nj39", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14086", "collection": "thesis", "collection_id": "14086", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02222021-054057067", "primary_object_url": { "basename": "Hybrid Si III-V Lasers for Next-generation Coherent Optical Communication.pdf", "content": "final", "filesize": 4976526, "license": "other", "mime_type": "application/pdf", "url": "/14086/1/Hybrid Si III-V Lasers for Next-generation Coherent Optical Communication.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Hybrid Si/III-V Lasers for Next-generation Coherent Optical Communication", "author": [ { "family_name": "Zhang", "given_name": "Zhewei", "orcid": "0000-0002-1211-7957", "clpid": "Zhang-Zhewei" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The most important application of semiconductor lasers is, without doubt, optical communication, the backbone of the information age. In the past few decades, incoherent optical communication with conventional semiconductor lasers, the III-V distributed feedback (DFB) lasers, has successfully fulfilled the global demand for the data rate. However, in order to support the rapidly growing Internet traffic of the 21st century, the transition from incoherent to coherent optical communication is inevitable, requiring new types of lasers, as the conventional III-V DFB lasers lack the phase coherence needed to serve as the light sources in coherent optical communication. The existent alternatives with high phase coherence are external cavity lasers (ECLs) and fiber lasers, whose high price and bulky size effectively thwart the upgrade of the current communication networks. This is the main motivation for us to develop high-coherence semiconductor lasers.
\r\n\r\nTo achieve the goal, we shall rethink and redesign semiconductor lasers. Advanced modern fabrication technology helps us to turn bold ideas into reality. Not only do we build semiconductor lasers on hybrid platforms, but also engineer elaborately the optical mode to enhance the lasers\u2019 phase coherence. The newly developed semiconductor lasers, hybrid Si/III-V lasers, are the core of the entire thesis. Their design principles, fabrication process, properties and performance in the coherent optical communication system will be presented and discussed. The experimental results show the Si/III-V lasers' superiority to their conventional counterparts.
\r\n\r\nAside from possessing high phase coherence, the Si/III-V lasers have great potential to be the light sources on the integrated photonic platforms. The fundamental obstacle thwarting photonic integration is optical feedback, to which the conventional semiconductor lasers are very sensitive. Without the protection provided by optical isolators, which unfortunately cannot be fabricated on chip, the performance of the conventional III-V DFB lasers could get significantly degraded by optical feedback. The Si/III-V lasers, with their built-in high-Q resonators, are very robust against optical feedback and can function properly in the isolator-free coherent optical communication systems. Thus, the cost of future optical networks can be further reduced by monolithically integrating passive photonic devices such as modulators and demodulators with the Si/III-V lasers.
\r\n\r\nFinally, all the studies centered on laser coherence trigger us to think deeply about the underlying relation between different means of characterizing laser coherence. A rigorous mathematical relation, the Central Relation, has been derived here, which not only unveils the fundamental relation between laser lineshape and frequency noise power spectral density (PSD) but also provides new methods of frequency noise controlling like optical filtering.
", "doi": "10.7907/y85t-nj39", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14140", "collection": "thesis", "collection_id": "14140", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05112021-170331252", "primary_object_url": { "basename": "Han_PhD_Thesis_Caltech_2021_May_11th.pdf", "content": "final", "filesize": 26607848, "license": "other", "mime_type": "application/pdf", "url": "/14140/1/Han_PhD_Thesis_Caltech_2021_May_11th.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Dielectric Metasurfaces for Integrated Imaging Devices and Active Optical Elements", "author": [ { "family_name": "Kwon", "given_name": "Hyounghan", "orcid": "0000-0002-9257-687X", "clpid": "Hyounghan-Kwon" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Optical dielectric metasurfaces have shown great advances in the last two decades and become promising candidates for next-generation free-space optical elements. In addition to their compatibility with scalable semiconductor fabrication technology, metasurfaces have provided new and efficient ways to manipulate diverse characteristics of light. In this thesis, we demonstrate the potential of dielectric metastructures in the realization of compact imaging devices, reconfigurable optical elements, and multi-layer inverse-designed metasurfaces. With the metasurfaces\u2019 extreme capability to simultaneously control phase and polarization, we first showcase their potential toward optical field imaging applications. In this regard, we demonstrate a system of dielectric metasurfaces and designed random metasurfaces for single-shot phase gradient microscopes and computational complex field imaging system, respectively. Then, we propose nano-electromechanically tunable resonant dielectric metasurfaces as a general platform for active metasurfaces. For example, we demonstrate two different types of the phase and amplitude modulators. While one utilizes resonant eigenmodes in the lattice such as leaky guided mode resonances and bound-states in the continuum modes, the other is based on the high-Q Mie resonances in the dielectric nanostructures where symmetry is broken. In addition to the modulation of the phase and amplitude, we also show tuning of strong chiroptical responses in dielectric chiral metasurfaces. Next, we experimentally demonstrate inverse-designed multi-layer metasurfaces. Not only do they provide increased degree of freedom in the design space, but also overcome limits of conventional design methods of the metasurfaces. Finally, we summarize the presented works and conclude this thesis with a brief outlook on what aspects of the metasurfaces can be important for their real-world applications in the future and what challenges and opportunities remain.
", "doi": "10.7907/j08n-0q77", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13845", "collection": "thesis", "collection_id": "13845", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08042020-093945451", "type": "thesis", "title": "From Metasurfaces to Compact Optical Metasystems", "author": [ { "family_name": "Faraji Dana", "given_name": "Mohammad Sadegh", "orcid": "0000-0002-8012-1253", "clpid": "Faraji-Dana-Mohammad-Sadegh" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical metasurfaces are a class of ultra-thin diffractive optical elements, which can control different properties of light such as amplitude, phase, polarization and direction at various wavelengths. The compatibility of optical metasurfaces with standard micro- and nano-fabrication processes makes them highly-suitable for realization of compact and planar form optical devices and systems. In addition, optical metasurfaces have achieved unique and unprecedented functionalities not possible by conventional diffractive or refractive optical elements. In this thesis, after a short review on the history and state of the art optical metasurfaces, I will discuss the systems consisting of optical metasurfaces, called optical meta-systems, which allow for implementations of complicated optical functions, such as wide field of view imaging and projection, tunable cameras, retro-reflection, phase-imaging, multi-color imaging, etc. Thereafter, the concept of folded metasurface optics is introduced and a compact folded metasurface spectrometer is showcased to demonstrate how the folded meta-systems can be designed, fabricated and practically utilized for real-life applications. Furthermore, different approaches for implementation of miniaturized hyperspectral imagers are investigated, among which the folded metasurface optics and a computational scheme using a random metasurface mask will be highlighted. Other potentials of optical metasurfaces achieved by the employment of optimization techniques to improve their multi-functional performances, as well as example applications in realizing optical vortex cornographs are studied. Finally, I will conclude the dissertation with an outlook on further applications of optical metasurfaces, where they can surpass the performance of current optical devices and systems and what limitations are still to be overcome before we can expect their wide-spread applications in our daily life.
", "doi": "10.7907/kvsy-ve81", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13845", "collection": "thesis", "collection_id": "13845", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08042020-093945451", "type": "thesis", "title": "From Metasurfaces to Compact Optical Metasystems", "author": [ { "family_name": "Faraji Dana", "given_name": "Mohammad Sadegh", "orcid": "0000-0002-8012-1253", "clpid": "Faraji-Dana-Mohammad-Sadegh" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical metasurfaces are a class of ultra-thin diffractive optical elements, which can control different properties of light such as amplitude, phase, polarization and direction at various wavelengths. The compatibility of optical metasurfaces with standard micro- and nano-fabrication processes makes them highly-suitable for realization of compact and planar form optical devices and systems. In addition, optical metasurfaces have achieved unique and unprecedented functionalities not possible by conventional diffractive or refractive optical elements. In this thesis, after a short review on the history and state of the art optical metasurfaces, I will discuss the systems consisting of optical metasurfaces, called optical meta-systems, which allow for implementations of complicated optical functions, such as wide field of view imaging and projection, tunable cameras, retro-reflection, phase-imaging, multi-color imaging, etc. Thereafter, the concept of folded metasurface optics is introduced and a compact folded metasurface spectrometer is showcased to demonstrate how the folded meta-systems can be designed, fabricated and practically utilized for real-life applications. Furthermore, different approaches for implementation of miniaturized hyperspectral imagers are investigated, among which the folded metasurface optics and a computational scheme using a random metasurface mask will be highlighted. Other potentials of optical metasurfaces achieved by the employment of optimization techniques to improve their multi-functional performances, as well as example applications in realizing optical vortex cornographs are studied. Finally, I will conclude the dissertation with an outlook on further applications of optical metasurfaces, where they can surpass the performance of current optical devices and systems and what limitations are still to be overcome before we can expect their wide-spread applications in our daily life.
", "doi": "10.7907/kvsy-ve81", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13946", "collection": "thesis", "collection_id": "13946", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09092020-162015646", "type": "thesis", "title": "Optical Light Manipulation and Imaging Through Scattering Media", "author": [ { "family_name": "Xu", "given_name": "Jian", "orcid": "0000-0002-4743-2471", "clpid": "Xu-Jian" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Chen", "given_name": "Yanbei", "orcid": "0000-0002-9730-9463", "clpid": "Chen-Yanbei" }, { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Typical optical systems are designed to be implemented in free space or clean media. However, the presence of optical scattering media scrambles light waves and becomes a problem in light field control, optical imaging, and sensing.
\r\n\r\nTo address the problem caused by optical scattering media, we discuss two types of solutions in this thesis. One type of solution is active control, where active modulators are used to modulate the light wave to compensate the wave distortion caused by optical scattering. The other type of solution is computational optics, where physical and mathematical models are built to computationally reconstruct the information from the measured distorted wavefront.
\r\n\r\nIn the part of active control, we first demonstrate coherent light focusing through scattering media by transmission matrix inversion. The transmission matrix inversion approach can realize coherent light control through scattering media with higher fidelity compared to conventional transmission matrix approaches. Then, by combining the pre-designed scattering metasurface with wavefront shaping, we demonstrate a beam steering system with large angular and high angular resolution. Next, we present optical-channel-based intensity streaming (OCIS), which uses only intensity information of light fields to realize light control through scattering media. This solution can be used to control spatially incoherent light propagating through scattering media. In the part of computational optics, we first demonstrate the idea of interferometric speckle visibility spectroscopy (ISVS) to measure the information cerebral blood flow. In ISVS, a camera records the speckle frames of diffused light from the human subject interferometrically, and the speckle statistics is used to calculate the speckle decorrelation time and consequently the blood flow index. Then, we compare the two methods of decorrelation time measurements - temporal sampling methods and spatial ensemble methods - and derive unified mathematical expressions for them in terms of measurement accuracy. Based on current technology of camera sensors and single detectors, our results indicate that spatial ensemble methods can have higher decorrelation time measurement accuracy compared to commonly used temporal sampling methods.
", "doi": "10.7907/4hkq-dz43", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13955", "collection": "thesis", "collection_id": "13955", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09172020-190836007", "primary_object_url": { "basename": "Thesis_Ghazaleh_Kafaie_Shirmanesh_09_16_2020.pdf", "content": "final", "filesize": 15346384, "license": "other", "mime_type": "application/pdf", "url": "/13955/7/Thesis_Ghazaleh_Kafaie_Shirmanesh_09_16_2020.pdf", "version": "v9.0.0" }, "type": "thesis", "title": "Electro-Optically Tunable Metasurfaces for a Comprehensive Control of Properties of Light", "author": [ { "family_name": "Kafaie Shirmanesh", "given_name": "Ghazaleh", "orcid": "0000-0003-1666-3215", "clpid": "Kafaie-Shirmanesh-Ghazaleh" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The ability to control electromagnetic wavefront is a central key in optics. Conventional optical components rely on the gradual accumulation of the phase of light as it passes through an optical medium. However, since the accumulated phase is limited by the permittivity of naturally existing materials, such a mechanism often results in bulky devices that are much thicker than the operating wavelength.
\r\n\r\nDuring the last several years, metasurfaces (quasi-2D nanophotonic structures) have attracted a great deal of attention owing to their promise to manipulate constitutive properties of electromagnetic waves such as amplitude, phase, and polarization. Metasurfaces are ultrathin arrays of subwavelength resonators, called meta-atoms, where each meta-atom imposes a predefined change on the properties of the scattered light. By precisely designing the optical response of these meta-atoms to an incident wave, metasurfaces can introduce abrupt changes to the properties of the transmitted, reflected, or scattered light, and hence, can flexibly shape the out-going wavefront at a subwavelength scale. This enables metasurfaces to replace conventional bulky optical components such as prisms or lenses by their flat, low-profile analogs. Furthermore, a single metasurface can perform optical functions typically attained by using a combination of multiple bulky optical elements, offering tremendous opportunities for flat optics.
\r\n\r\nThe optical response of a metasurface is typically dictated by the geometrical parameters of the subwavelength scatterers. As a result, most of the reported metasurfaces have been passive, namely have functions that are entirely fixed at the time of fabrication. By making the metasurfaces reconfigurable in their phase, amplitude, and polarization response, one can achieve real-time control of optical functions, and indeed, achieve multi-functional characteristics after fabrication. Dynamical control of the properties of the scattered light is possible by using external stimuli such as electrical biasing, optical pumping, heating, or elastic strain that can give rise to changes in the dielectric function or physical dimensions of the metasurface elements.
\r\n\r\nIn this dissertation, we present the opportunities and challenges towards achieving reconfigurable metasurfaces. We introduce a paradigm of active metasurfaces for real-time control of the wavefront of light at a subwavelength scale by investigating different modulation mechanisms and possible metasurface designs and material platforms that let us effectively employ the desired modulation mechanism. We will present multiple electro-optically tunable metasurface platforms. These electronically-tunable schemes are of great interest owing to their robustness, high energy-efficiency, and reproducibility. We will also show the design and experimental demonstration of active metasurfaces for which the tunable optical response can be tailored in a pixel-by-pixel configuration.
\r\n\r\nThe ability to individually control the optical response of metasurface elements has made active optical metasurfaces to be progressively ubiquitous by enabling a wide range of optical functions such as dynamic holography, light fidelity (Li-Fi), focusing, and beam steering. As a result, reconfigurable metasurfaces can hold an extraordinary promise for optical component miniaturization and on-chip photonic integration. Such compact and high-performance devices with reduced size, weight, and power (SWaP) can be used in future free-space optical communications or light detection and ranging (LiDAR) systems.
", "doi": "10.7907/m554-as73", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13955", "collection": "thesis", "collection_id": "13955", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09172020-190836007", "primary_object_url": { "basename": "Thesis_Ghazaleh_Kafaie_Shirmanesh_09_16_2020.pdf", "content": "final", "filesize": 15346384, "license": "other", "mime_type": "application/pdf", "url": "/13955/7/Thesis_Ghazaleh_Kafaie_Shirmanesh_09_16_2020.pdf", "version": "v9.0.0" }, "type": "thesis", "title": "Electro-Optically Tunable Metasurfaces for a Comprehensive Control of Properties of Light", "author": [ { "family_name": "Kafaie Shirmanesh", "given_name": "Ghazaleh", "orcid": "0000-0003-1666-3215", "clpid": "Kafaie-Shirmanesh-Ghazaleh" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The ability to control electromagnetic wavefront is a central key in optics. Conventional optical components rely on the gradual accumulation of the phase of light as it passes through an optical medium. However, since the accumulated phase is limited by the permittivity of naturally existing materials, such a mechanism often results in bulky devices that are much thicker than the operating wavelength.
\r\n\r\nDuring the last several years, metasurfaces (quasi-2D nanophotonic structures) have attracted a great deal of attention owing to their promise to manipulate constitutive properties of electromagnetic waves such as amplitude, phase, and polarization. Metasurfaces are ultrathin arrays of subwavelength resonators, called meta-atoms, where each meta-atom imposes a predefined change on the properties of the scattered light. By precisely designing the optical response of these meta-atoms to an incident wave, metasurfaces can introduce abrupt changes to the properties of the transmitted, reflected, or scattered light, and hence, can flexibly shape the out-going wavefront at a subwavelength scale. This enables metasurfaces to replace conventional bulky optical components such as prisms or lenses by their flat, low-profile analogs. Furthermore, a single metasurface can perform optical functions typically attained by using a combination of multiple bulky optical elements, offering tremendous opportunities for flat optics.
\r\n\r\nThe optical response of a metasurface is typically dictated by the geometrical parameters of the subwavelength scatterers. As a result, most of the reported metasurfaces have been passive, namely have functions that are entirely fixed at the time of fabrication. By making the metasurfaces reconfigurable in their phase, amplitude, and polarization response, one can achieve real-time control of optical functions, and indeed, achieve multi-functional characteristics after fabrication. Dynamical control of the properties of the scattered light is possible by using external stimuli such as electrical biasing, optical pumping, heating, or elastic strain that can give rise to changes in the dielectric function or physical dimensions of the metasurface elements.
\r\n\r\nIn this dissertation, we present the opportunities and challenges towards achieving reconfigurable metasurfaces. We introduce a paradigm of active metasurfaces for real-time control of the wavefront of light at a subwavelength scale by investigating different modulation mechanisms and possible metasurface designs and material platforms that let us effectively employ the desired modulation mechanism. We will present multiple electro-optically tunable metasurface platforms. These electronically-tunable schemes are of great interest owing to their robustness, high energy-efficiency, and reproducibility. We will also show the design and experimental demonstration of active metasurfaces for which the tunable optical response can be tailored in a pixel-by-pixel configuration.
\r\n\r\nThe ability to individually control the optical response of metasurface elements has made active optical metasurfaces to be progressively ubiquitous by enabling a wide range of optical functions such as dynamic holography, light fidelity (Li-Fi), focusing, and beam steering. As a result, reconfigurable metasurfaces can hold an extraordinary promise for optical component miniaturization and on-chip photonic integration. Such compact and high-performance devices with reduced size, weight, and power (SWaP) can be used in future free-space optical communications or light detection and ranging (LiDAR) systems.
", "doi": "10.7907/m554-as73", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13957", "collection": "thesis", "collection_id": "13957", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09182020-074010855", "type": "thesis", "title": "Active Flat Optics Wavefront Manipulation for Imaging, Ranging, and Sensing", "author": [ { "family_name": "Fatemi", "given_name": "Seyed Mohammadreza", "orcid": "0000-0001-9081-2608", "clpid": "Fatemi-Seyed-Mohammadreza" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The emergence and maturity of integrated photonic platforms over the past decade allowed for reliable integration of a large number of photonic components on a single substrate. This ability to process and control coherent light on a chip is a potential pathway for the realization of novel low-cost systems capable of non-conventional functionalities for optical wavefront engineering. In this thesis, integrated active flat optics architectures for generation, manipulation, and reception of optical wavefronts are investigated. In particular, the application of such systems for imaging, ranging, and sensing are studied and multiple photonic systems including a large scale transmitter, a high-sensitivity receiver, and a high-resolution transceiver are demonstrated.
\r\n\r\nFor generation of optical wavefronts, solutions for engineering a radiative optical waveform via emission by an array of nano-photonic antennas are studied and a chip-scale photonic transmitter is implemented. The transmitter forms an optical phased array with a novel architecture in a CMOS compatible silicon photonics process which not only dispenses with the limitations of previously demonstrated systems but also yields a narrower beamwidth leading to a higher resolution. Moreover, an integrated adaptive flat optical receiver architecture that collects samples of the incident light and processes it on-chip with high detection sensitivity is implemented. To detect the optical samples with a high signal to noise ratio, an optoelectronic mixer is proposed and designed that down-converts the optical signals received by each antenna to a radio frequency signal in the electronic domain, provides conversion gain, and rejects interferers. This system allows arbitrary wavefront manipulation of the received signal by adapting itself to new conditions \u2014 a capability that does not exist in conventional cameras. Using this system, we realized the first high-sensitivity optical phased array receivers with one-dimensional and two-dimensional apertures and the functionality of the chips as ultra-thin lens-less cameras were demonstrated. To achieve a high-resolution integrated photonic 3D imager with low system complexity, a double spectral sampling method is developed through a special wavefront sampling arrangement on the transmitter and receiver apertures. This transceiver architecture includes a multi-beam transmitter and a high-sensitivity receiver that can distinguish the illuminated points separately and process them simultaneously using a digital signal processor.
\r\n\r\nMoreover, novel ultra-low power architectures for generation and reception of short RF/microwave pulses are explored. Such systems have a broad range of applications including imaging and ranging. In this study, the capability of generating and receiving orthogonal Hermite pulses of various orders using a capacitor-only time-varying network is demonstrated.
", "doi": "10.7907/7e5p-9r23", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13978", "collection": "thesis", "collection_id": "13978", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10162020-115452109", "type": "thesis", "title": "Investigation of Transport Phenomena of Thermal Acoustic Excitations in Semi-Crystalline and Amorphous Materials Using Transient Grating Spectroscopy", "author": [ { "family_name": "Kim", "given_name": "Taeyong", "orcid": "0000-0003-2452-1065", "clpid": "Kim-Taeyong" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "thesis_committee": [ { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The physics of transport of heat-carrying atomic vibrations in amorphous and semi-crystalline solids is a topic of fundamental interest. Diverse tools have been employed to study thermal transport in these materials, including cryogenic thermal conductivity measurements and various inelastic scattering tools. However, unambiguously identifying the damping mechanisms of few THz and smaller frequency excitations remains difficult owing to the lack of the experimental probes in the frequency band. As a result, debate has remained regarding the microscopic origin of weak acoustic damping in amorphous silicon (Si), the unusually high thermal conductivity of ultra-drawn polyethylene, and other topics.
\r\n\r\nIn this thesis, we investigate the transport properties of heat-carrying acoustic excitations in semi-crystalline and amorphous solids using transient grating spectroscopy. This optical method permits the creation of thermal gradients over sub-micron length scales which may be comparable to the attenuation lengths of the excitations. We show how these measurements can be used to constrain the damping mechanisms in the sub-THz range that has been historically inaccessible by typical methods such as inelastic scattering.
\r\n\r\nFirst, we report measurements of the bulk thermal conductivity and elastic properties of MoS\u2082 thin films. Specifically, we use TG to measure the in-plane longitudinal sound velocity and thermal conductivity. We do not observe any size effects of thermal conductivity with grating period, indicating that the propagating distance of heat-carrying acoustic phonons are smaller than the thermal length scale accessible in the experiment. This result is consistent with the mean free paths predicted from ab-initio numerical methods.
\r\n\r\nSecond, we utilize the capability of TG to resolve the microscopic heat transport properties of phonons in highly oriented semi-crystalline polyethylene (PE). Earlier experimental studies have reported thermal conductivities of up to ~ 100 Wm\u207b\u00b9 K\u207b\u00b9 crystalline polyethylene, orders of magnitude larger than the bulk value of ~ 0.4 Wm\u207b\u00b9 K\u207b\u00b9. However, the microscopic origin of the high thermal conductivity remains unclear. We address this question by applying TG to highly oriented polyethylene to show that mean free paths on micron length scales are the dominant heat carriers. Using a low-energy anisotropic Debye model to interpret these data, we find evidence of one-dimensional phonon density of states for excitations of frequency less than ~ 2 THz. This transition frequency is consistent with the unique features of ultradrawn PE, in particular the stiff longitudinal branch leading to wavelengths of 8 nm at 2 THz frequency; and fiber diameters < 10 nm observed in prior structural studies of ultradrawn polymers; so that the wavelength does indeed exceed the fiber diameter at the relevant frequencies.
\r\n\r\nFinally, we report the measurements of the frequency-resolved mean free path of heat-carrying acoustic excitation in amorphous silicon (aSi), for the first time. The heat-carrying acoustic excitations of amorphous silicon are of interest because their mean free paths approach the micron scale at room temperature. Despite extensive investigation, the origin of the weak acoustic damping in the heat-carrying frequencies remains a topic of debate for decades. A prior study suggested a framework of classifying the vibrations into propagons, diffusons, and locons. Propagons were considered phonon-like, delocalized, propagating vibrations; locons as localized vibrations, and diffusons as delocalized yet non-propagating vibrations. Following the framework, numerous works have predicted mechanism of acoustic damping in aSi, but the predictions have contradicted to observations in experiments. In this work, we obtained measurements of the frequency-dependent mean free path in amorphous silicon thin films from ~0.1-3 THz and over temperatures from 60 - 315 K using picosecond acoustics (PSA) and transient grating spectroscopy. We first describe our PSA experiments to resolve the attenuation of 0.1 THz acoustic excitations in aSi. We then present our table-top approach to resolve MFP of heat-carrying acoustic excitation between ~ 0.1-3 using TG spectroscopy. The mean free paths are independent of temperature and exhibit a Rayleigh scattering trend over most of this frequency range. The observed trend is inconsistent with the predictions of numerical studies based on normal mode analysis, but agrees with diverse measurements on other glasses. The micron-scale MFPs in amorphous Si arise from the absence of Akhiezer and two-level system damping in the sub-THz frequencies, leading to heat-carrying acoustic excitations with room-temperature damping comparable to that of other glasses at cryogenic temperatures. Our results allow us to establish a clear picture for the origin of micron-scale damping in aSi by understanding vibrations as acoustic excitation rather than propagons, diffusons, and locons.
", "doi": "10.7907/k364-ga14", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14203", "collection": "thesis", "collection_id": "14203", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05292021-053844660", "type": "thesis", "title": "Applications and Integration of Optical Frequency Combs", "author": [ { "family_name": "Shen", "given_name": "Boqiang", "orcid": "0000-0003-0697-508X", "clpid": "Shen-Boqiang" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Leifer", "given_name": "Stephanie D.", "orcid": "0000-0002-8980-7825", "clpid": "Leifer-Stephanie-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical frequency combs have a wide range of applications in science and technology, including but not limited to timekeeping, optical frequency synthesis, spectroscopy, searching for exoplanets, ranging, and microwave generation. The integration of microresonator with other photonic components enables the high-volume production of wafer-scale optical frequency combs, soliton microcombs. However, it faces two considerable obstacles: optical isolation, which is challenging to integrate on-chip at acceptable performance levels, and power-hungry electronic control circuits, which are required for the generation and stabilization of soliton microcombs. In this thesis, we describe the design and early commissioning of the laser frequency comb for astronomical calibration using electro-optic modulation. We also focus on the realization of a novel and compact chip-scale optical frequency comb, soliton microcomb, including the progress made towards the visible soliton microcomb generation and the demonstration of low power operation of a soliton microcomb along contours of constant power in the phase space. We introduce a soliton spectrometer using dual-locked counter-propagating soliton microcombs to provide high-resolution frequency measurement. Finally, we look into the integration of lasers and high-Q microresonators. The self-injection locking process has been shown to create a new turnkey soliton operating point that eliminates difficult-to-integrate optical isolation as well as complex startup and feedback loops. Moreover, this technique also simplifies the access to high-efficiency dark soliton states without special dispersion engineering of microresonators.", "doi": "10.7907/p5z5-n346", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:11768", "collection": "thesis", "collection_id": "11768", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08282019-141610693", "primary_object_url": { "basename": "Hybrid_Devices_For_Scalable_Quantum_Systems.pdf", "content": "final", "filesize": 111473193, "license": "other", "mime_type": "application/pdf", "url": "/11768/1/Hybrid_Devices_For_Scalable_Quantum_Systems.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Integrating Quantum Optical and Superconducting Circuits with Quantum Acoustics for Scalable Quantum Network and Computation", "author": [ { "family_name": "Luo", "given_name": "Jie", "orcid": "0000-0002-6464-2761", "clpid": "Luo-Jie" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Austin", "given_name": "Joanna M.", "orcid": "0000-0003-3129-5035", "clpid": "Austin-J-M" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_eng" } ], "abstract": "Due to its high coherence in transmission over a large distance in the ambient environment, the quantum optical system has been a prevailing platform for long-distance quantum communication, which was recently realized over a continental distance with a low earth orbit satellite and ground stations [102, 70]. However, the pure quantum optical system has so far shown weak interactions between photon and matter, which makes it inefficient in carrying out deterministic quantum gates for quantum repeater based scalable quantum network and quantum computing. On the other hand, superconducting quantum systems operating in the microwave domain with Josephson junction transmon qubits have proven to be capable of efficient deterministic quantum operations on quantum states [86, 87, 66]. Nevertheless, such architecture is prone to errors and decoherence due to cross-talk between microwave elements in a large-scale superconducting quantum circuit. Furthermore, superconducting systems, in general, also have large footprint (100s um) elements (resonators and superconducting quantum bits) [92, 60] that limit the ability to scale up a superconducting quantum system. Moreover, microwave quantum circuits require cooling to around 10 mK, making it unsuitable for communicating quantum information outside a dilution refrigerator (DF). Micro- and nano- acoustic elements have been extensively used in conventional integrated information processing systems due to their compactness and high coherence [97]. Acoustic systems in quantum engineering also have the advantage of being a platform for universal couplings between various quantum systems including spins, optical photons, and superconducting circuits. As it will be discussed in this thesis, elements critical to scalable optical quantum network and superconducting quantum circuit can be constructed relying on the cavity optomechanics and piezoelectric interactions.
\r\n\r\nOptomechanical interaction is concerned with the light pressure coupling of cavity mechanical deformation to a strong optical \ufb01eld. This interaction has allowed the close to mechanical ground state cooling of mechanical resonators using laser and the ultra-sensitive displacement measurement that led to the detection of gravitational waves in the LIGO collaboration [125, 25]. Optomechanical crystals (OMCs) are lithographically patterned devices which contain a periodic structure that host bandgaps for both optical band electromagnetic waves and microwave band acoustic waves. A properly engineered defect in the crystal can con\ufb01ne and localize acoustic and electromagnetic modes of similar wavelengths into a small mode volume [17, 20, 21]. A strong optomechanical coupling, which can be achieved between such strongly con\ufb01ned co-localized optical and acoustic modes, can be used in engineering the quantum state of mechanical motion to realize useful quantum devices such as a high-coherence quantum memory [74] and an optomechanical high efficiency optical isolator for unidirectionally connecting distant optical cavities via an acoustic bus [37].
\r\n\r\nTo strongly couple the mechanical degree of freedom with a superconducting quantum circuit, various methods can be used, ranging from electromechanic coupling (electric coupling to a mechanically compliant capacitor), magnetomechanical coupling (magnetic coupling to a vibrating SQUID loop), and piezoelectric coupling. The recent advent of quantum acoustics [23, 8, 9] was realized with the strong piezoelectric coupling between a superconducting transmon qubit and a high-coherence mechanical resonator. The engineered strong piezoacoustic coupling provides the possibility to carry out deterministic ultra-high \ufb01delity two-qubit quantum gates on non-classical mechanical quantum states [52]. This ability together with the recent demonstration of ultra-long phonon lifetime mechanical resonators show the possibility of integrating the ultra-high quality mechanical resonator as a compact quantum memory element and even a new ultra-compact (10s um) quantum bit architecture for scalable superconducting quantum circuits. Furthermore, the strong piezoelectric coupling that can transduce quantum state in a superconducting circuit into mechanical wave also makes it possible to efficiently transduce a quantum state between a superconducting quantum circuit and a telecommunication band optical channel via a mechanical waveguide connected to an optomechanical crystal cavity.
\r\n", "doi": "10.7907/P0YC-CQ43", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13613", "collection": "thesis", "collection_id": "13613", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01092020-141256074", "type": "thesis", "title": "Boundary Integral Equation Methods for Simulation and Design of Photonic Devices", "author": [ { "family_name": "Garza Gonzalez", "given_name": "Emmanuel", "orcid": "0000-0003-1687-8216", "clpid": "Garza-Gonzalez-Emmanuel" } ], "thesis_advisor": [ { "family_name": "Bruno", "given_name": "Oscar P.", "clpid": "Bruno-O-P" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Owhadi", "given_name": "Houman", "clpid": "Owhadi-H" }, { "family_name": "Sideris", "given_name": "Constantine", "clpid": "Sideris-Constantine" }, { "family_name": "Bruno", "given_name": "Oscar P.", "clpid": "Bruno-O-P" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents novel boundary integral equation (BIE) and associated optimization methodologies for photonic devices. The simulation and optimization of such structures is a vast and rapidly growing engineering area, which impacts on design of optical devices such as waveguide splitters, tapers, grating couplers, and metamaterial structures, all of which are commonly used as elements in the field of integrated photonics. The design process has been significantly facilitated in recent years on the basis of a variety of methods in computational electromagnetic (EM) simulation and design. Unfortunately, however, the expense required by previous simulation tools has limited the extent and complexity of the structures that can be treated. The methods presented in this thesis represent the results of our efforts towards accomplishing the dual goals of 1) Accurate and efficient EM simulation for general, highly-complex three-dimensional problems, and 2) Development of effective optimization methods leading to an improved state of the art in EM design.
\r\n\r\nOne of the main proposed elements utilizes BIE in conjunction with a modified-search algorithm to obtain the modes of uniform waveguides with arbitrary cross sections. This method avoids spurious solutions by means of a certain normalization procedure for the fields within the waveguides. In order to handle problems including nonuniform waveguide structures, we introduce the windowed Green function (WGF) method, which used in conjunction with auxiliary integral representations for bound mode excitations, has enabled accurate simulation of a wide variety of waveguide problems on the basis of highly accurate and efficient BIE, in two and three spatial dimensions. The \"rectangular-polar\" method provides the basic high-order singular-integration engine. Based on non-overlapping Chebyshev-discretized patches, the rectangular-polar method underlies the accuracy and efficiency of the proposed general-geometry three-dimensional BIE approach. Finally, we introduce a three-dimensional BIE framework for the efficient computation of sensitivities \u2014 i.e. gradients with respect to design parameters \u2014 via adjoint techniques. This methodology is then applied to the design of metalenses including up to a thousand parameters, where the overall optimization process takes in the order of three hours using five hundred computing cores. Forthcoming work along the lines of this effort seeks to extend and apply these methodologies to some of the most challenging and exciting design problems in electromagnetics in general, and photonics in particular.
", "doi": "10.7907/XXPX-9H78", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13673", "collection": "thesis", "collection_id": "13673", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04122020-055837611", "primary_object_url": { "basename": "CW_thesis.pdf", "content": "final", "filesize": 175792073, "license": "other", "mime_type": "application/pdf", "url": "/13673/115/CW_thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "On-Chip Photonic Devices for Coupling to Color Centers in Silicon Carbide", "author": [ { "family_name": "Wang", "given_name": "Chuting", "orcid": "0000-0002-3711-682X", "clpid": "Wang-Chuting" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical quantum networks are important for global use of quantum computers, and secure quantum communication. Those networks require storage devices for synchronizing or making queues of processing transferred quantum information. Practical quantum information networks should minimize loss of transmitted data (photons) and have high efficiency mapping when writing data on memories (solid state qubits). This requires strong light-matter interaction that is enabled by coupling qubits to optical cavities.
\r\n\r\nThe first half of the thesis focuses on emerging candidates for promising qubits in silicon carbide (SiC). The optical and quantum properties of these color centers are discussed with focus on divacancies in 4H-SiC due to their long spin coherence time. Optically detected magnetic resonance of divacancies is shown, an essential technique for reading out the qubit state using the intensity of optical emission.
\r\n\r\nThe second half of the thesis focuses on hybrid photonic devices for coupling to silicon carbide qubits. Hybrid devices are made of another layer of high refractive index material other than the qubit hosting material. Evanescent coupling to qubits close to the surface can be achieved without damaging the host material. Mainly the silicon (Si) on 4H-SiC hybrid ring resonator architecture is discussed starting from design, simulation to fabrication. The fabrication includes Si membrane transfer that is an important step to create a light confining layer on 4H-SiC. The final ring resonator device shows quality factors as high as 23000.
", "doi": "10.7907/m2p0-6t37", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13639", "collection": "thesis", "collection_id": "13639", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02122020-151048251", "primary_object_url": { "basename": "Ng_Ryan_2020.pdf", "content": "final", "filesize": 20979784, "license": "other", "mime_type": "application/pdf", "url": "/13639/1/Ng_Ryan_2020.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Nanophotonic Phenomena in Dielectric Photonic Crystals", "author": [ { "family_name": "Ng", "given_name": "Ryan Cecil", "orcid": "0000-0002-0527-9130", "clpid": "Ng-Ryan-Cecil" } ], "thesis_advisor": [ { "family_name": "Greer", "given_name": "Julia R.", "clpid": "Greer-J-R" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Shapiro", "given_name": "Mikhail G.", "clpid": "Shapiro-M-G" }, { "family_name": "Brady", "given_name": "John F.", "clpid": "Brady-J-F" }, { "family_name": "Greer", "given_name": "Julia R.", "clpid": "Greer-J-R" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_chem" } ], "abstract": "Photonic crystals are periodic optical nanostructures with varying dielectric constant that allow light flow to be controlled and manipulated much in a similar way to electrons within a semiconductor crystal. These nanostructures tend to have a spatially varying refractive index on the order of the wavelength of light to be manipulated. 1D and 2D photonic crystals have already garnered significant attention in the realm of thin-film optics, while 3D photonic crystals have been thus far limited in application, due to difficulties in fabrication and a lack of available materials for fabrication.
\r\n\r\nIn this work, we first explore 1D and 2D photonic crystals based on the concept of a guided mode resonance, which manifests as a narrow near-unity resonance in reflection or transmission that arise from the coupling of an incident wave into a leaky waveguide mode via a grating vector that is subsequently re-radiated. Such a resonance is well-suited for multi- and hyper- spectral filtering applications in the infrared. We designed a platform consisting of amorphous Si arrays embedded in SiO2 in simulation and experiment for application as narrow stopband filters. We present the tunability of the spectral characteristics of the resonance in these arrays through variation of array geometric parameters in simulation and experiment. Guided mode resonance designs often consider only the case of an infinite array, where the leaky waveguide mode can propagate laterally for hundreds of periods, allowing for this mode to eventually scatter out of the array giving rise to the characteristic narrow near-unity rapid spectral variations of a GMR. With an insufficient number of periods, the quality factor and thus the optical filtering performance is greatly diminished. Thus, we further extend our analysis to compact periodic arrays of finite size, which are required for high spatial resolution snapshot imaging, and introduce array designs that operate under finite size limitations in the near-infrared.
\r\n\r\nWe then transition to 3D photonic crystals, exploring the use of an additive manufacturing process to directly fabricate nanocrystalline rutile TiO2 with ~100 nm resolution. Though TiO2 was chosen as the model material, the key to this work is that a similar process can be used to print many different materials, enabling future applications of 3D photonic crystals. The focus here is the additive manufacturing of high index materials such as TiO2, and its potential for photonic applications is demonstrated by characterizing the optical band gap of 3D PhC TiO2 structures printed with this method. We present a system where the ability to print high refractive index 3D photonic crystals would be useful, by studying 3D polymer-germanium core-shell structures that should exhibit all-angle negative refraction in the mid-infrared regime.
", "doi": "10.7907/ZP30-F550", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13798", "collection": "thesis", "collection_id": "13798", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06082020-144243454", "type": "thesis", "title": "Cavity Optomechanics for Hybrid Quantum Systems", "author": [ { "family_name": "Ren", "given_name": "Hengjiang", "orcid": "0000-0002-5612-8287", "clpid": "Ren-Hengjiang" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Recent advances in optomechanical systems have led to a series of scientific and technical advances. In addition, they have demonstrated macroscopic quantum phenomena, including probabilistic preparation of quantum states, squeezed light, and coherent transduction between photons with different energies. There are advantages in using phonons within a quantum information network. Within the solid state, all optical and electronic phenomena strongly depend on the local distortions of the crystal lattice, i.e. mechanical phonons, hence could connect dissimilar degrees of freedom such as superconducting qubits operating at gigahertz frequencies with atomic/optical states. Also, unlike photons, phonons do not radiate into free space. Energy damping of phonon can occur through radiation into bulk structure which support the mechanical resonator, through impurities and defects in the material, and due to the inherent anharmonic motion of atoms within solid-state materials.
\r\n\r\nIn this thesis, we explore the limits of acoustic damping and coherence of a microwave-frequency acoustic nanocavity with a phononic crystal shield that possesses a wide bandgap for all polarizations of acoustic waves. The nanocavity is formed from an optomechanical crystal (OMC) nanobeam resonator. It supports an acoustic breathing mode at ~ 5 GHz and a co-localized telecom optical resonant mode which allows us to excite and readout mechanical motion using radiation pressure from a pulsed laser source. This minimally invasive pulsed measurement technique avoids a slew of parasitic damping effects - typically associated with electrode materials and mechanical contact, or probe fields for continuous readout - and allows for the sensitive measurement of motion at the single phonon level. The results of acoustic ringdown measurements at millikelvin temperatures show that damping due to radiation is effectively suppressed by the phononic shield, with breathing mode quality factors reaching mechanical quality factor Q = 4.9 x 1010, corresponding to an unprecedented frequency-Q product of f-Q = 2.6 x 1020 and an effective phonon propagation length of several kilometers. Measurement of the frequency jitter of the acoustic resonance is also performed, indicating telegraph-like noise corresponding to a coherence time of ~ 130 \u00b5s. The observed breathing mode behavior can be explained by TLS interactions when taking into account the highly modified density of phonon states in the shielded OMC cavity, which are most likely present in the amorphous etch-damaged region of the silicon surface. In particular, we find that damping due to nearly resonant TLS is suppressed due to the bandgap of the phononic shield, and that relaxation damping from non-resonant TLS can explain the magnitude, low temperature dependence of the breathing mode damping, and lack of saturation of the damping with both temperature and acoustic amplitude.
\r\n\r\nThe extremely small motional mass and narrow linewidth of the OMC cavity make it ideal for precision mass sensing and in exploring limits to alternative quantum collapse models.
\r\n\r\nOur mechanical modes exist in the same frequency range as common superconducting qubits, suggesting a possibility for creating a hybrid quantum architecture consisting of acoustic and superconducting quantum circuits, where the small scale, reduced cross-talk, and ultralong coherence time of quantum acoustic devices may provide significant improvements in connectivity and performance of current quantum hardware. A proposal of mechanical quantum memory based on ultra-high-Q mechanical model and piezo-electrical coupling is also discussed in this work. \r\nOne remaining roadblock, which significantly compromises the utility of OMCs integration with superconducting circuits, is the very weak, yet non-negligible parasitic optical absorption, which is thought to occur due to surface defect states, and together with inefficient thermalization can yield significant heating of the hypersonic mechanical mode of the device at ultralow temperatures, where microwave systems can be reliably operated as quantum devices. In 1D OMC experiments, the quantum cooperativity (Ceff), which corresponds to the standard photon-phonon cooperativity divided by the Bose factor of the thermal bath and is the most relevant figure-of-merit for operation of optomechanical systems at ultralow temperatures, was lower than unity for all but a microsecond around the time an optical pulse is applied. This limits quantum optomechanical experiments to schemes with short pulses. Increased Ceff can be achieved with improved thermalization, for example, by employing a two-dimensional (2D) OMC cavity.
\r\n\r\nIn this thesis, we demonstrate an improved silicon quasi-2D OMC with an over 50-fold improvement in back-action per photon over previous reports. We are able to measure the dynamics of the internal cavity acoustic modes of both 1D nanobeam and quasi-2D OMCs. Quasi-2D OMC shows much lower bath occupancy compared to 1D structures. Most importantly, quasi-2D OMCs demonstrated a Ceff greater than unity under steady-state optical pumping, a crucial threshold for realizing a variety of optomechanical applications. For example, bi-directional transduction or amplification of continuous quantum signals require the optomechanical device to be operated in a continuous mode. An analysis of piezo-optomechanical bi-directional microwave to optics transducer is also presented in this thesis.
", "doi": "10.7907/vr67-w986", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13759", "collection": "thesis", "collection_id": "13759", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012020-134801698", "primary_object_url": { "basename": "Craiciu_Ioana_2020.pdf", "content": "final", "filesize": 33061620, "license": "other", "mime_type": "application/pdf", "url": "/13759/1/Craiciu_Ioana_2020.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Quantum Storage of Light Using Nanophotonic Resonators Coupled to Erbium Ion Ensembles", "author": [ { "family_name": "Craiciu", "given_name": "Ioana", "orcid": "0000-0002-8670-0715", "clpid": "Craiciu-Ioana" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "This thesis presents on-chip quantum storage of telecommunication wavelength light using nanophotonic resonators coupled to erbium ions. Storage of light in an optical quantum memory has applications in quantum information and quantum communication. For example, long distance quantum communication using quantum repeater protocols is enabled by quantum memories. Efficient and broadband quantum memories can be made from resonators coupled to ensembles of atoms. Like other rare earth ions, erbium is appealing for quantum applications due to its long optical and hyperfine coherence times in the solid state at low temperatures. However, erbium is unique among rare earth ions in having an optical transition in the telecommunication C band (1540 nm), making it particularly appealing for quantum communication applications. In this work, we use nano-scale resonators coupled to erbium-167 ions in yttrium orthosilicate crystals (167Er 3+:Y2SiO5).
\r\n\r\nWe demonstrate quantum storage in two types of resonators. In a nanobeam photonic crystal resonator milled directly in 167Er 3+:Y2SiO5, we show storage of weak coherent states using the atomic frequency comb protocol. The storage fidelity for single photon states is estimated to be at least 93.7% ± 2.4% using decoy state analysis, Storage of up to 10 μs and multimode storage are demonstrated. Using a hybrid amorphous silicon 167Er 3+:Y2SiO5 resonator and on-chip electrodes, we demonstrate a multifunctional memory using the atomic frequency comb protocol with DC Stark shift control. In addition dynamic control of memory time, Stark shift control allows modifications to the frequency and bandwidth of stored light. We show tuning of the output pulse by ± 20 MHz relative to the input pulse, and broadening of the pulse bandwidth by more than a factor of three. The storage efficiency in both devices was limited to < 1%.
\r\n\r\nOn the way to these results, we describe 167Er 3+:Y2SiO5 spectroscopy measurements including optical coherence times and hyperfine lifetimes below 1 K, and we estimate the linear DC stark shift along two crystal directions. The design and fabrication of the on-chip resonators is presented. We discuss the limitations to storage time and efficiency, including superhyperfine coupling and resonator parameters, and we outline a path forward for improving the storage efficiency in these types of devices.
", "doi": "10.7907/yn6n-7x40", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13755", "collection": "thesis", "collection_id": "13755", "cite_using_url": "https://resolver.caltech.edu/CaltechThesis:06012020-093627645", "primary_object_url": { "basename": "Tokpanov_Yury_2020.pdf", "content": "final", "filesize": 18652320, "license": "other", "mime_type": "application/pdf", "url": "/13755/1/Tokpanov_Yury_2020.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Towards Next Generation of Optoelectronics: from Quantum Plasmonics and 2D Materials to Advanced Optimization Techniques of Nanophotonic Devices", "author": [ { "family_name": "Tokpanov", "given_name": "Yury", "orcid": "0000-0001-5123-7428", "clpid": "Tokpanov-Yury" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Yue", "given_name": "Yisong", "clpid": "Yue-Yisong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this thesis, we explore different novel concepts and materials for the next-generation of nanophotonic and optoelectronic devices that could be used both in classical and quantum settings.
\r\n\r\nFirst, we study quantum coherence properties of surface plasmon polaritons (SPPs) in the regime of extreme dispersion. Most experiments to date, that tested quantum coherence properties of SPPs, used essentially weakly-confined plasmons, which experience limited light-matter hybridization, thus restricting the potential for decoherence. Our setup is based on a hole-array chip supporting SPPs near the surface plasma frequency, where plasmonic dispersion and confinement is much stronger than in previous experiments, making the plasmons much more susceptible for decoherence processes. We generated polarization-entangled pairs of photons and transmitted one of the photons through this plasmonic hole array. Our results show that the quality of photon entanglement after the highly-dispersive plasmonic channel is unperturbed. Our findings provide a lower bound of 100 femtoseconds for the pure dephasing time of dispersive plasmons in our materials, and show that even in a highly dispersive regime, surface plasmons preserve quantum mechanical correlations, making possible harnessing the power of extreme light confinement for integrated quantum photonics.
\r\n\r\nSecond, we systematically study different passivation schemes of sulfur vacancies in 2D molybdenum disulfide using first-principles calculations based on density functional theory. We aim at building a microscopic understanding of passivation mechanisms of treatment with TFSI superacid - a popular approach of to improve optical properties. Since superacids have a strong ability to donate protons, we consider hydrogenation and protonation of sulfur vacancies as a possible passivation scheme. Our calculations show that effects of protonation and hydrogenation on properties of 2D molybdenum disulfide are very similar. Moreover, we find that four hydrogen atoms can fully \"heal\" sulfur vacancies in this material. Our results are an important step towards controllable defects design in 2D transition metal dichalcogenides.
\r\n\r\nAnd third, we study applications of advanced methods of optimization and machine learning to the design of different nanophotonic devices. We explore feasibility of using novel multi-fidelity Gaussian processes optimization technique to optimize plasmonic mirror filters for hyperspectral imaging. We compare our results with other common optimization approaches. Then we apply deep-learning inspired techniques to optimize control voltages of individual pixels of active metasurfaces to achieve dynamic beamsteering. We obtain interesting results that pave the way for future experiments both in nanophotonics and machine learning fields.
", "doi": "10.7907/tg1b-hn35", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13753", "collection": "thesis", "collection_id": "13753", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312020-234931669", "type": "thesis", "title": "Using DNA Origami to Create Hybrid Nanophotonic Architectures for Single-Photon Emitters", "author": [ { "family_name": "Mitskovets", "given_name": "Anna", "orcid": "0000-0003-1967-5334", "clpid": "Mitskovets-Anna" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Rothemund", "given_name": "Paul W. K.", "clpid": "Rothemund-P-W-K" } ], "thesis_committee": [ { "family_name": "Gopinath", "given_name": "Ashwin", "clpid": "Gopinath-Ashwin" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Rothemund", "given_name": "Paul W. K.", "clpid": "Rothemund-P-W-K" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The limitations in physical dimensions of silicon transistors give us a stimulus to explore alternative systems for better computational performance. The most promising system that received a lot of attention in the past few years is a quantum computer. Ideally, a nanophotonic quantum computer would consist of hundreds of single-photon emitters, optical or plasmonic resonators, optical waveguides and interconnects. The main difficulty in large-scale production of such quantum photonic networks is the integration and deterministic coupling of single-photon sources to photonic elements.
\r\n\r\nIn the first part of this thesis, we utilize spontaneous parametric down-conversion to create correlated pairs of indistinguishable photons. These photons are generated by bismuth borate nonlinear crystal and then are coupled to a photonic chip where they interfere at directional couplers to produce a path-entangled state. Our photonic chip consists of waveguides, directional couplers, and a single Mach-Zender interferometer with a thermo-optic phase shifter. When a part of the waveguide connecting directional couplers is replace with a plasmonic waveguide, quantum state of photons is converted to plasmonic state. Here we report a measurement of path entanglement between surface plasmons with 95% contrast, confirming that a path-entangled state can indeed survive without measurable decoherence. Our measurement suggests that elastic scattering mechanisms of the type that might cause pure dephasing in plasmonic systems must be weak enough not to significantly perturb the state of the metal under the experimental conditions we investigated.
\r\n\r\nThe second part of this work is dedicated to the study of a novel DNA origami self-assembly technique for creating hybrid nanophotonic architectures to create single-photon emitters. DNA origami is a modular platform for the combination of molecular and colloidal components to create optical, electronic, and biological devices. We present a DNA origami molecule that can be deterministically positioned on a silicon chip within 3.2\u00b0 alignment. Orientation is absolute (all degrees of freedom are speci\ufb01ed) and arbitrary (every molecule\u2019s orientation is independently speci\ufb01ed). The use of orientation to optimize device performance is shown by aligning \ufb02uorescent emission dipoles within microfabricated optical cavities. Large-scale integration is demonstrated via an array of 3,456 DNA origami with 12 distinct orientations, which indicates the polarization of the excitation light. Following this experiment, we explore how many molecular emitters can be coupled to this DNA origami shape and discover interesting interactions between ssDNA extensions that can cause origami to fold along its seam. Finally, we examine DNA origami self-assembly methods that can be used to deterministically couple single-photon emitters to resonators in order to decrease pure-dephasing rates and increase indistinguishability of emitted photons.
", "doi": "10.7907/kqaj-ex65", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13750", "collection": "thesis", "collection_id": "13750", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312020-215457608", "type": "thesis", "title": "Suspended Trace Air-Gap Resonators for Low Loss Superconducting Circuits", "author": [ { "family_name": "Fang", "given_name": "Michael Tianyu", "orcid": "0000-0003-2321-1321", "clpid": "Fang-Michael-Tianyu" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Brandao", "given_name": "Fernando", "orcid": "0000-0003-3866-9378", "clpid": "Brand\u00e3o-F-G-S-L" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Quantum memories and networks for distributed quantum information processing require links between the microwave, mechanical, and optical domains. Coherent integration of long-lived superconducting qubits (SCQs) with optomechanical and photonic devices (OMPDs) remains an outstanding challenge. We present a step towards coherent integration using a suspended trace air-gap resonator (STAR): a superconducting resonator on a silicon-on-insulator (SOI) substrate with the signal trace suspended by silicon tethers above and between galvanically connected ground metal planes. As a result, the electric field energy is closely confined within the microwave structure, yielding lower crosstalk compared to conventional coplanar waveguides (CPW). An order of magnitude improvement in the quality factors for STAR over previous work on SOI is achieved, in a transverse cross-sectional area that is an order of magnitude more compact. Electric field participation in lossy bulk dielectrics, a dominant source of energy leakage in previous measurements of aluminum CPW resonators on SOI, is virtually eliminated in STAR. The loss from the metal-air interface now dominates, but can be reduced by several factors using superconductors with better surface properties. Most importantly, STAR fabrication is compatible with Josephson junction and air-bridge deposition for highly coherent integration of SCQs and OMPDs to realize proposals for quantum information storage and networking.
", "doi": "10.7907/6teq-md72", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:13748", "collection": "thesis", "collection_id": "13748", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312020-201105584", "primary_object_url": { "basename": "Allmaras_Thesis_Final.pdf", "content": "final", "filesize": 99904005, "license": "other", "mime_type": "application/pdf", "url": "/13748/8/Allmaras_Thesis_Final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Modeling and Development of Superconducting Nanowire Single-Photon Detectors", "author": [ { "family_name": "Allmaras", "given_name": "Jason Paul", "orcid": "0000-0001-9621-289X", "clpid": "Allmaras-Jason-Paul" } ], "thesis_advisor": [ { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Shaw", "given_name": "Matthew D.", "clpid": "Shaw-M-D" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Superconducting nanowire single-photon detectors (SNSPDs) have demonstrated remarkable efficiency, timing resolution, and intrinsic dark count rate properties, but the SNSPD community currently lacks a comprehensive model of the single-photon detection process. In this work, we conduct a detailed examination of the current detection mechanism models and compare their predictions to new experimental measurements of the intrinsic timing properties and polarization dependence of specialized NbN test devices. First, we consider the energy downconversion cascade using the kinetic equations to describe the non-equilibrium electron and phonon systems immediately following photon absorption. These calculations provide estimates for the energy loss and fluctuations during this process, and provide qualitative information about the way energy is partitioned between the electron and phonon systems. To study the suppression of superconductivity following downconversion, we apply the most advanced existing model, that of Vodolazov (2017), but find it inadequate to quantitatively describe the timing properties of these detectors. By extending the model to use the generalized time-dependent Ginzburg-Landau equations, we achieve better quantitative agreement with experiment. However, the generalized model still provides only a qualitative picture of the detection process.
\r\n\r\nWe also conduct an experimental examination of the heat transfer process in WSi nanowires by examining the nanowire reset dynamics, steady-state dissipation, and crosstalk between elements of an array. The results are compared to existing electrothermal models, but these models fail to adequately describe the dynamics of the system. A generalized form of the electrothermal model provides better fitting to experiment, but incorporation of non-equilibrium effects is likely needed to provide a fully quantitative description of the system. These results are directly connected to some of the thermal challenges of SNSPD array development. Informed by the crosstalk results, we demonstrate a new multiplexing technique based on thermal coupling between two active nanowire layers, known as the thermal row-column. This method promises to enable kilopixel to megapixel scale imaging arrays for low photon-flux applications. Finally, we discuss the design and characterization of the ground detector for the Deep Space Optical Communication (DSOC) demonstration mission.
", "doi": "10.7907/wgak-vs11", "publication_date": "2020", "thesis_type": "phd", "thesis_year": "2020" }, { "id": "thesis:11185", "collection": "thesis", "collection_id": "11185", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09172018-140652131", "primary_object_url": { "basename": "Fowler_thesis_Final_20180924.pdf", "content": "final", "filesize": 66566036, "license": "other", "mime_type": "application/pdf", "url": "/11185/12/Fowler_thesis_Final_20180924.pdf", "version": "v10.0.0" }, "type": "thesis", "title": "Silicon Neural Probes for Stimulation of Neurons and the Excitation and Detection of Proteins in the Brain", "author": [ { "family_name": "Fowler", "given_name": "Trevor Michael", "clpid": "Fowler-Trevor-Michael" } ], "thesis_advisor": [ { "family_name": "Roukes", "given_name": "Michael Lee", "orcid": "0000-0002-2916-6026", "clpid": "Roukes-M-L" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Roukes", "given_name": "Michael Lee", "orcid": "0000-0002-2916-6026", "clpid": "Roukes-M-L" }, { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Lester", "given_name": "Henry A.", "orcid": "0000-0002-5470-5255", "clpid": "Lester-H-A" }, { "family_name": "Moreaux", "given_name": "Laurent C.", "orcid": "0000-0003-1276-5062", "clpid": "Moreaux-Laurent-C" } ], "local_group": [ { "literal": "div_bbe" } ], "abstract": "This thesis describes the development of a number of novel microfabricated neural probes for a variety of specific neuroscience applications. These devices rely on single mode waveguides and grating couplers constructed from silicon nitride thin films, which allows the use of planar lightwave circuits to create advanced device geometries and functions. These probes utilize array waveguide gratings to select an individual emitter from a large array of emitters using the wavelength of incoming light, allowing for spatial multiplexing of optical stimulation. These devices were tested in the laboratory and in living tissue to verify their efficacy. This technology was then modified to create steerable beam forming for stimulation of neurons using optical phase arrays. This technology was also tested for use in fluoresence lifetime imaging microscopy and the first application of pulsed light through the photonic circuits. Finally, this technology was again modified to create laminar illumination patterns for light sheet fluorescence microscopy applications. These devices were further improved by adding embedded microfluidics to the probes. The process of creating embedded microfluidic channels by the dig and seal method is described in detail, including modifications to the procedure that were added to address potential pitfalls in the fabrication process. Next, two projects which combine microfluidics with the optical devices described in the previous chapter are detailed. One project involves combining the use of optical emitters with microfluidic injections containing caged neurotransmitters to stimulate neurons is described. The other project involves microfluidic sampling of the extracellular space for neuropeptides which are detected using ring resonator biosensors. The sensitivity of these biosensors was analyzed in detail, determining both the physical limit of detection and the effect of biological noise due to non-specific binding on the sensors.", "doi": "10.7907/2kvw-ad56", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11247", "collection": "thesis", "collection_id": "11247", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10252018-150052650", "type": "thesis", "title": "Superconducting Electromechanical and Nanophotonic Devices for Quantum Measurement and Conversion", "author": [ { "family_name": "Kalaee", "given_name": "Mahmoud", "clpid": "Kalaee-Mahmoud" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Microscale and nanoscale mechanical resonators have been used in advanced technological applications, from high precision time keeping and mass sensing, to processing high frequency signals in mobile communications. In the last few decades, they have been an important part of progress in the field of quantum information and metrology and have been proposed as quantum memories or transducers for measuring or connecting different types of quantum systems.
\r\n\r\nThe field of cavity optomechanics and electromechanics is concerned with coupling the electromagnetic field of a resonant optical cavity or electrical circuit to mechanical motion. These systems provide potential means to control and engineer the state of a mechanical object at the quantum level. This thesis contains the description of mechanical systems in megahertz to a few hundred megahertz frequency range formed by nano-fabricating photonic, phononic, and electrical circuits on a chip. These structures are designed to provide a large radiation pressure coupling between mechanical motion and electromagnetic fields to address and manipulate motional degrees of freedom. Qualitatively novel quantum effects are expected when one takes a step beyond linear coupling and exploits higher order interactions. To that end, we integrate electrical, mechanical and photonic structures in a multimode photonic crystal structure to observe \"x2-coupling\", where the optical cavity frequency is coupled to the square of the mechanical displacement. Moreover, we have developed two integrated on-chip platforms based on Si3N4 and Si nanomembranes capable of interfacing superconducting qubits and optical photons and realizing reversible microwave-to-optical conversion. We employ radiation pressure to cool these mechanical resonators to their quantum ground state. Finally, we demonstrate a form of electromechanical crystal for coupling microwave photons and hypersonic phonons of frequency \u03c9m/2\u03c0 = 0.425 GHz by capacitively coupling a phononic crystal acoustic cavity to a superconducting microwave resonator. Moving to higher frequency acoustic cavities not only facilitates the integration of electromechanical circuits and nanophotonic systems capable of operation in the resolved sideband limit of optomechanics for noise-free quantum signal conversion, but it opens up the possibility of using phonons as information carriers via phononic circuits. Utilizing a two-photon resonance condition for efficient microwave pumping and phononic bandgap shield to eliminate acoustic radiation, we achieve large cooperative electromechanical coupling (C \u2248 30) and intrinsic decay time of 2.3 ms. Moreover, electrical read-out of the phonon occupancy shows that the acoustic mode thermalizes close to its quantum ground-state of motion (phonon occupancy nm=1.5) at a fridge temperature of Tf = 10 mK. We conclude by considering several designs and fabrication improvements to the hypersonic electromechanical crystals that would enable them to perform quantum conversion between the electrical and acoustic\r\ndomain.
\r\n", "doi": "10.7907/3PMX-2Y88", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11417", "collection": "thesis", "collection_id": "11417", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03082019-114637094", "primary_object_url": { "basename": "Thesis_Gregory_MacCabe.pdf", "content": "final", "filesize": 69862958, "license": "other", "mime_type": "application/pdf", "url": "/11417/1/Thesis_Gregory_MacCabe.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Phonon Dynamics and Damping in Three-Dimensional Acoustic Bandgap Cavity-Optomechanical Resonators", "author": [ { "family_name": "MacCabe", "given_name": "Gregory Scott", "orcid": "0000-0003-2369-1580", "clpid": "MacCabe-Gregory-Scott" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Endres", "given_name": "Manuel A.", "orcid": "0000-0002-4461-224X", "clpid": "Endres-M" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_pma" } ], "abstract": "Mechanical resonators are used in a wide variety of technical applications, from precision time keeping and sensing, to the delay and filtering of microwave signals in mobile communication systems. Critical to many of these applications is the ability of a mechanical object to store vibrational energy at a well defined frequency of oscillation and with minimal damping. Energy damping can occur through acoustic radiation into the resonator support structure, or through impurities and defects in the resonator material, and is highly dependent on the temperature of operation due to the inherent anharmonic motion of atoms within solid-state materials. Here, we present optical measurements down to milliKelvin temperatures of the acoustic mode properties of a crystalline silicon nanobeam cavity incorporating a three-dimensional phononic bandgap support structure for acoustic confinement. Utilizing pulsed laser light to excite a co-localized optical mode of the optomechanical crystal (OMC) device, we are able to measure the dynamics of the internal cavity acoustic modes which are coupled to the light field via radiation pressure. These measurements represent an almost ideal scenario in which the ringdown occurs free of any additional mechanical or probe field contact, and where elastic scattering or radiation of the acoustic field does not lead to energy damping due to the full bandgap shield. The resulting ringdown measurements for the fundamental 5 GHz acoustic mode of the cavity show an exponential increase in phonon lifetime versus phononic shield period number, which at a bath temperature of 35 milliKelvin saturates above six periods to a value as long as 1.5 seconds. This ultra-long lifetime, corresponding to an effective phonon propagation length of several kilometers, is found at the lowest temperatures to be consistent with damping from non-resonant tunneling states whose energy lies below the acoustic shield phononic bandgap, and which are most likely present in the amorphous etch-damaged region of the silicon surface. Other, more rapid forms of damping such as resonant tunneling state damping or three-phonon scattering are suppressed due to the phononic bandgap shield and the reduced density of phonon states in the effectively one-dimensional nanobeam geometry. Prospects for newapplications of ultra-coherent nanoscale mechanical resonators include tests of various collapse models of quantum mechanics, or, if appropriately integrated with microwave superconducting quantum circuits, as miniature quantum memory or processing units with potentially many-orders of magnitude longer coherence time than their electromagnetic counterparts.
", "doi": "10.7907/7R9W-EV53", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11421", "collection": "thesis", "collection_id": "11421", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03132019-062905529", "primary_object_url": { "basename": "Kindem_Jonathan_2019.pdf", "content": "final", "filesize": 18204037, "license": "other", "mime_type": "application/pdf", "url": "/11421/1/Kindem_Jonathan_2019.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Quantum Nanophotonics with Ytterbium in Yttrium Orthovanadate", "author": [ { "family_name": "Kindem", "given_name": "Jonathan Miners", "orcid": "0000-0002-7737-9368", "clpid": "Kindem-Jonathan-Miners" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Hutzler", "given_name": "Nicholas R.", "clpid": "Hutzler-N-R" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Quantum light-matter interfaces that can reversibly map quantum information between photons and atoms are essential for building future quantum networks. Crystals doped with rare-earth ions (REIs) are an attractive solid-state platform for such light-matter interfaces due to their exceptional optical and spin coherence properties at cryogenic temperatures. Building scalable REI-based technology has proven to be challenging due to the inherently weak coupling of REIs with light. This thesis explores the integration of REIs with nanophotonic resonators to overcome this weak light-matter interaction and enable efficient, scalable quantum light-matter interfaces. Specifically, this work focuses on the development of quantum nanophotonics with ytterbium in yttrium orthovanadate.
\r\n \r\nThis thesis begins with an introduction to a nanophotonic platform based on photonic crystal cavities fabricated directly in rare-earth host materials and highlights the initial successes of this platform with neodymium-doped materials. This motivates an examination of the optical and spin coherence properties of 171Yb:YVO4, a REI material that was previously unexplored for quantum technology applications. This material is found to have strong optical transitions compared to other REI-doped materials, a simple energy level structure, and long optical and spin coherence lifetimes.
\r\n\r\nThe focus then turns to the detection and coherent manipulation of single ytterbium ions coupled to nanophotonic cavities. The Purcell-enhancement in these cavities enables efficient optical detection and spin initialization of individual ytterbium ions. We identify ions corresponding to different isotopes of ytterbium and show that the coupling of electron and nuclear spin in ytterbium-171 at zero-field gives rise to strong electron-spin-like transitions that are first-order insensitive to magnetic field fluctuations. This allows for coherent microwave control and the observation of long spin coherence lifetimes at temperatures up to 1 K. We then make use of the optical selection rules and energy structure of 171Yb:YVO4 to demonstrate high-fidelity single-shot optical readout of the spin state. These results establish nanophotonic devices in 171Yb:YVO4 as a promising platform for solid-state quantum light-matter interfaces.
", "doi": "10.7907/Q40T-8907", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11604", "collection": "thesis", "collection_id": "11604", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022019-011156429", "primary_object_url": { "basename": "Caltech_Thesis_Jeremy_Thesis_Graphene_Mediated_Light_Matter_Interaction.pdf", "content": "final", "filesize": 9794403, "license": "other", "mime_type": "application/pdf", "url": "/11604/1/Caltech_Thesis_Jeremy_Thesis_Graphene_Mediated_Light_Matter_Interaction.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Graphene-Mediated Light-Matter Interaction", "author": [ { "family_name": "Brouillet", "given_name": "Jeremy Jean", "orcid": "0000-0001-6664-5643", "clpid": "Brouillet-Jeremy-Jean" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Advances in 2D materials have opened a wealth of possibilities for the control of emission and propagation of light on length scales much smaller than the wavelength of light. Graphene, with highly-confined electrostatically tunable plasmons, provides a strong platform for explore a number of avenues.
\r\n\r\nWe show that graphene that can increase the luminescence of erbium by 80%, can induce population inversion in a three-level system, speed up the response time by over an order of magnitude, and has modulation depth of up to 14 dB for luminescence.
\r\n\r\nWe experimentally demonstrated a tunable epsilon-near-zero metamaterial with a elliptic-to-hyperbolic transition. The device had been theorized for many years and we provide the first experimental realization.
\r\n\r\nWe explore the properties of an isotropic tunable 2D heterostructure composed of black phosphorus, hexagonal boron nitride, and graphene. These symmetry-breaking materials create an effective permittivity that is biaxially anistropic and tunable. This material supports tunable beam steering based on propagation of energy along the hyperbolic dispersion lines.
", "doi": "10.7907/VRFE-ZY57", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11697", "collection": "thesis", "collection_id": "11697", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06062019-155629104", "type": "thesis", "title": "Light Emission and Ultrafast Carrier Dynamics in III-V Semiconductors from First Principles", "author": [ { "family_name": "Jhalani", "given_name": "Vatsal A.", "orcid": "0000-0003-0866-0858", "clpid": "Jhalani-Vatsal-A" } ], "thesis_advisor": [ { "family_name": "Bernardi", "given_name": "Marco", "orcid": "0000-0001-7289-9666", "clpid": "Bernardi-Marco" } ], "thesis_committee": [ { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" }, { "family_name": "Bernardi", "given_name": "Marco", "orcid": "0000-0001-7289-9666", "clpid": "Bernardi-Marco" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Goddard", "given_name": "William A., III", "orcid": "0000-0003-0097-5716", "clpid": "Goddard-W-A-III" } ], "local_group": [ { "literal": "Resnick Sustainability Institute" }, { "literal": "div_eng" } ], "abstract": "The III-V semiconductors are a broad class of technologically important materials which have seen immense research interest in academia and industry due to their electronic, optoelectronic, and photovoltaic properties. In particular, GaN and the III-nitride family of wide bandgap semiconductors have emerged as promising candidates for the next generation of high-efficiency power electronics and light-emitting devices. Their device operation and macroscopic properties are governed by the dynamics of charge carriers and their microscopic scattering processes. Near room temperature, the carriers are scattered by lattice vibrations (phonons) at ultrafast timescales of order fs-ps. Microscopic understanding of carrier dynamics is challenging due to both the ultrafast time scale at play and to the presence of defects, interfaces, and impurities affecting transport and spectroscopy measurements. Typical theoretical treatments of carrier dynamics and light emission employ empirical models to interpret and fit experimental results. Over the last few years, so-called first-principles (or \"ab initio\") methods to accurately compute ultrafast carrier dynamics, transport, and light emission have seen a rapid rise. These approaches do not employ parameters from experiments, and using only the structure of the material as input, together with quantum mechanics and condensed matter theory, are enabling accurate predictions of carrier dynamics in a wide range of materials and are shedding light on microscopic details such as which electronic states, phonon modes and dissipative processes are responsible for the observed charge transport and light emission properties.
\r\n\r\n\r\nHere, we present first-principles calculations of different aspects of ultrafast carrier dynamics and light emission in III-V semiconductors of technological relevance, focusing on GaN, a key material for solid-state light emission technology. We first present a study of the ultrafast nonequilibrium dynamics of excited (so-called \"hot\") carriers in GaN, with a focus on electron-phonon scattering and the nanometer scale transport of carriers in GaN light emitting devices (LEDs). Using cutting-edge first-principles methods developed in this work, we find an asymmetry between the time scale of hot electron and hole thermalization which provides a possible explanation on a major open problem in the efficiency and energy losses of GaN LEDs. We then develop and apply a new rigorous first-principles approach for computing light emission and the radiative recombination lifetimes in bulk crystals, nanomaterials and isolated systems. Our approach is based on the Bethe-Salpeter equation (BSE), and it accurately includes excitons, namely electron-hole states bound by the Coulomb interaction that play a key role in light-matter interactions. Using this method, we carry out benchmark calculations of radiative lifetimes in GaAs and GaN. In GaN, our computed radiative lifetimes are in excellent agreement with experiment (within a factor of two), and our calculations further highlight the importance of including excitonic effects and spin-orbit coupling to obtain accurate radiative. We also employ a model to account for exciton thermal dissociation at high temperature, finding excellent agreement with spectroscopic measurements. Lastly, we discuss ongoing work on computing the intrinsic (phonon-limited) mobility in bulk GaN from first principles, focusing on efforts to include piezoelectric electron-phonon interactions, which are important for acoustic phonon modes in GaN. We compute the electron and hole mobilities in GaN and obtain excellent agreement with experiment. Our calculations shed light on which phonon modes scatter the carriers, providing new microscopic insight into charge carrier dynamics in GaN and related III-V semiconductors.
", "doi": "10.7907/9E0D-KX54", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11481", "collection": "thesis", "collection_id": "11481", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04222019-151834122", "type": "thesis", "title": "Metasurfaces: Beyond Diffractive and Refractive Optics", "author": [ { "family_name": "Arbabi", "given_name": "Ehsan", "orcid": "0000-0002-5328-3863", "clpid": "Arbabi-Ehsan" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Optical metasurfaces are a category of thin diffractive optical elements, fabricated using the standard micro- and nano-fabrication techniques. They provide new ways of controlling the flow of light based on various properties such as polarization, wavelength, and propagation direction. In addition, their compatibility with standard micro-fabrication techniques and compact form factor allows for the development of several novel platforms for the design and implementation of various complicated optical elements and systems. In this thesis, I first give a short overview and a brief history of the works on optical metasurfaces. Then I discuss the capabilities of metasurfaces in controlling the polarization and phase of light, and showcase their potential applications through the cases of polarimetric imaging and vectorial holography. Then, a discussion of the chromatic dispersion in optical metasurfaces is given, followed by three methods that can be utilized to design metasurfaces working at multiple discrete wavelengths. As a potential application of such metasurfaces, I present results of using them as objective lenses in two-photon microscopy. In addition, I discuss how metasurfaces enable the at-will control of chromatic dispersion in diffractive optical elements, demonstrate metasurfaces with controlled dispersion, and provide a discussion of their limitations. Integration of multiple metasurfaces into metasystems allows for implementation of complicated optical functions such as imaging and spectrometry. In this regard, I present several examples of how such metasystems can be designed, fabricated, and utilized to provide wide field of view imaging and projection, microelectromechanically tunable lenses, optical spectrometers, and retroreflectors. I conclude with an outlook on where metasurfaces can be most useful, and what limitations should be overcome before they can find wide-spread application.
", "doi": "10.7907/EQEY-KZ52", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11508", "collection": "thesis", "collection_id": "11508", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05112019-120905666", "primary_object_url": { "basename": "Mahsa_thesis_5_8_2019.pdf", "content": "final", "filesize": 142818215, "license": "other", "mime_type": "application/pdf", "url": "/11508/2/Mahsa_thesis_5_8_2019.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Dielectric Metasurfaces from Fundamentals to Applications", "author": [ { "family_name": "Kamali", "given_name": "Seyedeh Mahsa", "orcid": "0000-0002-6968-811X", "clpid": "Kamali-Seyedeh-Mahsa" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Wang", "given_name": "Lihong", "clpid": "Wang-Lihong" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "In the past few decades, the advancements in nanotechnology have significantly altered many fields of science and technology, especially electronics and integrated photonics. Free-space optics, on the other hand, has remained mostly unaffected, and even today \"optics\" reminds us of carefully shaped and polished pieces of various types of glasses and crystals lumped into lenses and beam shapers. Several of these devices are then combined into more complicated optical systems like microscopes and pulse shapers that are expensive, bulky, sensitive to various environmental factors, and require several alignment steps. This thesis contains my work on designing and utilizing structures engineered at the nano-scale, which are called metasurfaces, to implement compact optical elements and systems with capabilities beyond those of conventional refractive and diffractive optics. My contributions to this field are two-fold: I have developed and contributed to the development of new concepts that take metasurfaces beyond conventional difractive optics in various aspects, in addition to paradigm changing platforms for optical element and system design. Here, I first give an overview and a brief history about optical metasurfaces. Next I discuss the unprecedented capabilities of metasurfaces in controlling light based on its degrees of freedom like illumination angle and polarization. Then, I will focus on various novel metasurface platforms of conformal and tunable metasurfaces, 3D metasurface beam shapers, and integrated metasurfaces. I conclude with an outlook on future potentials and challenges that need to be overcome for realizing their wide-spread applications.", "doi": "10.7907/TPN1-XA53", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11388", "collection": "thesis", "collection_id": "11388", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02102019-152730366", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 17563509, "license": "other", "mime_type": "application/pdf", "url": "/11388/1/Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Passive and Active Control of Radiative Heat Flow", "author": [ { "family_name": "Thomas", "given_name": "Nathan Hoover", "orcid": "0000-0003-4648-5325", "clpid": "Thomas-Nathan-Hoover" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" } ], "thesis_committee": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Greer", "given_name": "Julia R.", "clpid": "Greer-J-R" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Materials that control the absorption and emission of thermal radiation have attracted renewed interest for energy applications. Materials of interest include those with static optical properties that vary with photon wavelength in a desired manner as well as those with dynamic properties that can be actively tuned by external stimuli. The research in this thesis focuses on creating materials in both categories.
\r\n\r\nFirst, we examine selective absorbers for solar thermal energy conversion with high absorptivity in solar wavelengths and low emissivity in infrared wavelengths. Achieving stagnation temperatures exceeding 200 \u00b0C with unconcentrated sunlight, pertinent to technologies like industrial process heat, air conditioning, and electricity generation, requires better spectrally selective absorbers with ultra-low thermal emittance. Current state-of-art surfaces are based on ceramic-metal mixtures and patterned metal or metal-dielectric structures. Semiconductor based selective surfaces with near zero absorption below the bandgap offer the potential for lower thermal emittance than that achieved with such surfaces that employ metals in the primary absorbing medium. In this thesis, we report a semiconductor-based multilayer selective absorber that exploits the sharp drop in optical absorption at the band gap energy to achieve a measured absorptance of 76% at solar wavelengths and a low emittance of approximately 5% at thermal wavelengths. In field tests, we obtain a peak temperature of 225 \u00b0C, comparable to that achieved with state-of-the-art selective surfaces. With straightforward optimization to improve solar absorption, our work shows the potential for unconcentrated solar thermal systems to reach stag- nation temperatures exceeding 300 \u00b0C, higher than any available selective surface. Our surface would eliminate the need for solar concentrators for mid-temperature solar applications such as supplying process heat.
\r\n\r\nSecond, we theoretically propose and experimentally implement a thermal switch for near-field radiative transfer. In the field of active thermal materials for manipulating heat flow in a controllable and reversible manner, numerous approaches to perform thermal switching have been reported. However, they typically suffer from various limitations, including small switching ratio or requiring large temperature differentials. We report the experimental implementation of a scheme to electrostatically control near-field radiative transfer in a graphene field effect heterostructure. We measure a maximum heat flux modulation of 4 \u00b1 3% and an absolute heat flux modulation rate of 24 \u00b1 7 mWm\u22122 per V bias. Employing gate dielectrics with lower surface warp and higher dielectric breakdown strength as well as reducing conductive losses would enable modulations up to 100%, substantially exceeding the switching ratios achievable by other methods. Our work paves the way for electrostatic control of near-field radiative transfer using two-dimensional materials.
", "doi": "10.7907/FGWC-0244", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11524", "collection": "thesis", "collection_id": "11524", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05192019-220451795", "type": "thesis", "title": "Nonlinear Physics in Soliton Microcombs", "author": [ { "family_name": "Yang", "given_name": "Qifan", "orcid": "0000-0002-7036-1712", "clpid": "Yang-Qifan" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Bellan", "given_name": "Paul Murray", "clpid": "Bellan-P-M" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Like rulers of light, optical frequency combs consist of hundreds to millions of coherent laser lines, which are capable of measuring time and frequency with the highest degree of accuracy. Used to rely on table-top mode-locked lasers, optical frequency combs have been recently realized in a miniaturized form, namely the microcomb, using monolithic microresonators. Besides a reduction of footprint, microcombs could also achieve parity with traditional frequency combs in performance by mode-locking through the formation of \"light bullets\" called dissipative Kerr solitons. These soliton microcombs not only serve as a unique platform to study nonlinear physics, but also offer scalable and cost-effective solutions to many groundbreaking applications, spanning spectroscopy to time standards. In this thesis I will trace the physical origin of soliton microcombs, followed by their experimental realization in high-Q silica microresonators. The impact of several nonlinear process on solitons will be discussed, which leads to novel soliton systems, e.g., Stokes solitons and counter-propagating solitons. Utilizing these nonlinear properties, we show that soliton microcombs can be adapted for high-precision spectroscopic applications. In the end, a real-time method for monitoring transient behavior of solitons will be presented.", "doi": "10.7907/DWMX-S056", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:10554", "collection": "thesis", "collection_id": "10554", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11122017-215023206", "type": "thesis", "title": "Integrated Nonlinear Photonic Devices", "author": [ { "family_name": "Oh", "given_name": "Dong Yoon", "orcid": "0000-0001-6716-1851", "clpid": "Oh-Dong-Yoon" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_eng" } ], "abstract": "Chip-scale nonlinear optics can provide important new functions in communications, frequency metrology and spectroscopy. Optical microcavities enhance nonlinear optical effects through resonant recirculation. This recirculation dramatically reduces the required power in applications and also lowers signal noise. A key figure-of-merit is the optical Q factor, which provides a dimensionless scale of optical storage time within the microcavity. In this thesis, a novel integrated ultra-high-Q microcavity with Q as high as 230 million is presented. The device is applied to demonstrate multiple functions including electronic-rate soliton microcomb generation and stimulated Brillouin laser operation. For soliton generation, the resonator must be engineered to produce optical mode families that feature anomalous dispersion. This engineering is applied to generate solitons at wavelengths of 1064 nm and 778 nm. Systems-on-a-chip applications of these devices are discussed including compact optical synthesizers, optical clocks and rotation sensors. Finally, a compact array of silica ridge waveguides is described and applied for efficient and coherent ultraviolet-to-visible comb generation by dispersive-wave generation. Unlike other devices used to broaden spectra such as micro-structured fibers, these arrays provide a wide range of emission wavelength choices on a single chip. The arrays can also enable mode-locked lasers to attain greatly extended spectral reach for spectroscopy, bioimaging, tomography and metrology. ", "doi": "10.7907/Z95H7DGT", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10540", "collection": "thesis", "collection_id": "10540", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10262017-003847721", "type": "thesis", "title": "Frequency Noise Control of Heterogeneous Si/III-V Lasers ", "author": [ { "family_name": "Kim", "given_name": "Dongwan", "orcid": "0000-0002-5661-2503", "clpid": "Kim-Dongwan" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Narrow-linewidth lasers have many applications including optical telecommunication, laser spectroscopy, atomic clocks, and light detection and ranging. Conventionally, narrow linewidth lasers have been realized in the form of fiber-based or solid-state lasers. These lasers are bulky and relatively expensive, limiting their usage as bench-top systems in laboratory environments. Historically, semiconductor lasers, also known as laser diodes, have served applications where size and cost are important factors, including fiber optic communications. The linewidth of the semiconductor lasers, however, has been limited to the MHz-level, due to high loss in laser cavities and small size.
\r\n\r\nRecently, reduction of the frequency fluctuations in the semiconductor lasers has been achieved, obtaining tens of kHz linewidth, using the heterogeneous Silicon/III-V platform with a new design strategy. In this design, the majority of the optical energy is stored in the low-loss high-Q silicon resonator away from the high-loss III-V active region, requiring the minimal gain from the active region to overcome the reduced modal loss.
\r\n\r\nThis work explores the new design strategy further, and demonstrates theoretically and experimentally that the strategy eliminates the frequency fluctuations arising from the amplitude-phase coupling by placing a relaxation resonance frequency at frequencies of a few hundred MHz. Consequently, it becomes possible to obtain a semiconductor laser device possessing sub-kHz quantum-limited linewidths at frequencies of a few GHz (the frequencies of interest in optical telecommunication).
\r\n\r\nIn addition to the frequency noise reduction, the strategy turns out to have the additional benefit of accomplishing a coherent and stable lasing operation, even under external reflections. Thus, the new design strategy has the potential to replace the costly, but currently indispensable external optical isolators, which have been traditionally used to maintain the consistent performance of semiconductor lasers in the presence of external reflection.
\r\n\r\nThis work paves the way for the design of narrow-linewidth and stable semiconductor lasers that can function without the use of the bulky and costly external components, such as external cavities or optical isolators.
", "doi": "10.7907/Z90Z71G6", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10538", "collection": "thesis", "collection_id": "10538", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10242017-104926655", "type": "thesis", "title": "The Coherence Collapse Regime of High-Coherence Si/III-V Lasers and the Use of Swept Frequency Semiconductor Lasers for Full Field 3D Imaging", "author": [ { "family_name": "Harfouche", "given_name": "Mark", "orcid": "0000-0002-4657-4603", "clpid": "Harfouche-Mark" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The semiconductor laser is the linchpin of optical communication and is now also penetrating a wide spectrum of new applications such as biomedical sensing, coherent communication, metrology, and time keeping. These require a higher degree of temporal coherence than is available from the present generation. Recently, it has been proposed and shown that heterogeneously integrated lasers on silicon and InGaAsP can be used to design high coherence single mode lasers with a much narrower linewidth than their all InGaAsP counterparts. Unfortunately, these lasers suffer from large thermal impedances and their optical feedback characteristics have not yet been explored. In the first part of this thesis, we will explore how flip chip bonding can help decrease the thermal impedance of these lasers to improve their overall performance and show that these lasers can provide up to 20 dB of optical isolation compared to their all III-V counterparts.
\r\n\r\nIn the second part of this thesis, we will report on the use of commercially available semiconductor lasers, in conjunction with an optical modulator to obtain high-resolution tomographic images in one shot without any moving parts. The electronic control over the imaged depth of this novel tomographic imaging camera enables it to monitor arbitrary depth slices in rapid succession over a depth range limited only by the coherence length of the laser. Not only does this imaging modality acquire the transverse image intensity (x,y) distribution of the light reflected from a particular depth, but also the phase of the reflected light enabling imaging beyond the conventional depth of field of the lens. This has important implications in applications requiring high lateral resolution images where the shallow depth of field would often require mechanical scanning of the lens elements to change the imaged depth.
", "doi": "10.7907/Z9W66J07", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10442", "collection": "thesis", "collection_id": "10442", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09202017-124555409", "primary_object_url": { "basename": "Horie_Yu_2018.pdf", "content": "final", "filesize": 59827475, "license": "other", "mime_type": "application/pdf", "url": "/10442/1/Horie_Yu_2018.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Controlling the Flow of Light Using High-Contrast Metastructures", "author": [ { "family_name": "Horie", "given_name": "Yu", "orcid": "0000-0001-7083-1270", "clpid": "Horie-Yu" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "A new class of planar optical components and devices has emerged using subwavelength metastructures with a strong contrast in refractive indices. High-contrast metastructures have shown promises to manipulate optical fields in an extraordinary way and to replace conventional bulky optical elements by their low-profile analogs, typically with subwavelength-scale features. We elucidate the underlying principle, how these seemingly low-profile geometries render unique optical responses, using the coupled-mode analysis in a multimode waveguide. Moreover, strong field localization in high-index structures allows us to interpret each single element in the metastructures as a low-quality-factor resonator (or a localized scatterer), permitting us to realize designer surface that shapes phase, amplitude, and polarization of light in free space, also known as an optical metasurface. The remainder of the thesis is devoted to explore novel applications in optics using high-contrast metastructures. One of the particularly interesting applications is to use them in an optical resonator. Specifically, we demonstrate to incorporate high-contrast subwavelength grating reflectors and dielectric metasufaces in a vertical Fabry\u2013Perot cavity, and show that we can flexibly tune the resonance frequency by the subwavelength patterning. With this technique, we envision the realization of compact, on-chip spectrometers when integrating them on a photodetector array. Secondly, we investigate the use of high-contrast subwavelength gratings in visible wavelengths. We perform the optimization of their geometries and demonstrate a set of RGB color filters, down to near a micrometer in the pixel size. This platform exhibits unique performances such as high efficiency, angular insensitivity, and color tunability by the design. A novel device concept is also explored, where a high-contrast subwavelength grating reflector is integrated on a silicon platform to constitute an active resonant antenna, enabling high-speed, phase-dominant modulation by means of thermo-optic effect of silicon. We demonstrate an array of such active antennas, yielding a beam deflection capability. This justifies the robustness of our device design, enabling a large-scale integration of high-speed, phase-dominant spatial light modulators. Finally, we introduce a disorder-engineered metasurface in the context of wavefront shaping. Recently, wavefront shaping with disordered media has demonstrated optical manipulation capabilities beyond those of conventional optics, but translating this class of technology into a practical use has remained challenging due to enormous amounts of information needed to be characterized as the input-output responses. As a paradigm shift, we propose the use of disorder-engineered metasurface in wavefront shaping, where the disorder is programmatically designed and makes the system characterization-free prior to use. With this approach, we demonstrate high numerical aperture focusing in an extended volume as well as wide-field fluorescence imaging with unprecedented performances.
", "doi": "10.7907/Z94X5604", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10427", "collection": "thesis", "collection_id": "10427", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09112017-095117655", "type": "thesis", "title": "2D and 3D Photonic Crystals: Synthesis, Characterization and Topological Phenomenon\r ", "author": [ { "family_name": "Peng", "given_name": "Siying", "orcid": "0000-0002-1541-0278", "clpid": "Peng-Siying" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Refael", "given_name": "Gil", "clpid": "Refael-G" }, { "family_name": "Eisenstein", "given_name": "James P.", "clpid": "Eisenstein-J-P" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "Topological photonics has become an increasingly popular research topic in the field of nanophotonics in recent years. Topological phases of light provide opportunities to manipulate light propagation efficiently at the nanoscale volume. Performance of conventional optical elements are limited by back-reflection and bending losses, which hinder their prospect of large scale integration. Topological protection enables unidirectional excitation of edge states or surface states without leaking into the bulk, as well as suppression of scattering when encountering defects and corners. With such advantages, topological photonic elements may surpass conventional photonic\r\ndesign for future generations of ultra-compact efficient computing, imaging, and sensing applications. Due to limitations of fabrication and characterization techniques, previously experimental efforts on topological photonics have been carried out with 2D micron-scale optical design or at the microwave wavelength.
\r\n\r\nThis thesis contributes to the experimental development of topological photonics in two aspects: first, how to fabricate and characterize 3D photonic crystals and therefore extend topological protection into the 3D (Chapters 2-3); and second, how to realize nanoscale topological protection in the visible frequencies (chapters 4-6). Specifically, Chapter 2 reports fabrication of 3D single gyroid structures composed of a-Si and FTIR characterization of a photonic bandgap at the mid-infrared wavelength. This is the foundation to investigate more complex morphologies to introduce topologically nontrivial photonic states. Chapter 3 describe properties of\r\ndouble gyroid photonic crystals, followed by angle resolved characterization method in the mid-infrared. Double gyroid photonic crystals can be designed to possess quadratic degeneracy points, Weyl points, and line nodes. Since Weyl points have non-zero Chern numbers, surface states are topologically protected in double gyroid photonic crystals with parity breaking symmetry. The angle resolved characterization method could be utilize to resolve both Weyl points and surface states. Chapter 4 depicts design, fabrication, and characterization of Dirac-like surface plasmon dispersions in metallic nano-pillars. Chapter 5 presents experimental investigation\r\nof coupled silicon Mie resonators, which is the first step towards topological design based on inter-lattice sites coupling in the next chapter. Chapter 6 details photonic bandstructure from angle-resolved cathodoluminescence measurements. We analyze bandstructures collected from the bulk of trivially and topologically gapped lattices, as well as zigzag and arm-chaired edges of domain boundaries. Chapter 7 outlines a method to optically enhance dissociation of hydrazine molecules using ultraviolet plasmons, and attempts to use this method for low temperature GaN growth.
", "doi": "10.7907/Z9NZ85V2", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10764", "collection": "thesis", "collection_id": "10764", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03082018-161639906", "primary_object_url": { "basename": "Thesis_Papadakis_v2.pdf", "content": "final", "filesize": 56199250, "license": "other", "mime_type": "application/pdf", "url": "/10764/1/Thesis_Papadakis_v2.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Optical Response in Planar Heterostructures: From Artificial Magnetism to Angstrom-Scale Metamaterials", "author": [ { "family_name": "Papadakis", "given_name": "Georgia Theano", "orcid": "0000-0001-8107-9221", "clpid": "Papadakis-Georgia-Theano" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Daraio", "given_name": "Chiara", "clpid": "Daraio-C" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The idea of expanding the range of properties of natural substances with artificial matter was introduced by V. G. Veselago in 1967. Since then, the field of metamaterials has dramatically advanced. Man-made structures can now exhibit a plethora of extraordinary electromagnetic properties, such as negative refraction, optical magnetism, and super-resolution imaging. Typical metamaterial motifs include split ring resonators, dielectric and plasmonic particles, fishnet and wire arrays. The principle of operation of these elements is now well-understood, and they are being exploited for practical applications on a global scale, ranging from telecommunications to sensing and biomedicine, in the radio frequency and terahertz domains. Accessing and controlling optical and near-infrared phenomena requires scaling down the dimensions of meta- materials to the nanometer regime, pushing the limits of state-of-the-art nano- lithography and requiring structurally less complex geometries. Hence, within the last decade, research in metamaterials has revisited a simpler, lithography- free structure, particularly planar arrangements of alternating metal and dielectric layers, termed hyperbolic metamaterials. Such media are readily realizable with well-established thin-film deposition techniques. They support a rich canvas of properties ranging from surface plasmonic propagation to negative refraction, and they can enhance the photoluminescence properties of quantum emitters at any frequency range.
\r\n\r\nHere, we introduce a computational approach that allows tailoring the dielectric and magnetic effective properties of planar metamaterials. Previously, planar hyperbolic metamaterials have been considered non-magnetic. In contrast, we show theoretically and experimentally that planar arrangements com- posed of non-magnetic constituents can be engineered to exhibit a non-trivial magnetic response. This realization simplifies the structural requirements for tailoring optical magnetism up to very high frequencies. It also provides access to previously unexplored phenomena, for example artificially magnetic plasmons, for which we perform an analysis on the basis of available materials for achieving polarization-insensitive surface wave propagation. By combining the concept of metamaterials\u2019 homogenization with previous transfer matrix approaches, we develop a general computational method for surface waves calculations that is free of previous assumptions, for example infinite or purely periodic media. Furthermore, we theoretically demonstrate that hyperbolic metamaterials can be dynamically tunable via carrier injection through external bias, using transparent conductive oxides and graphene, at visible and infrared frequencies, respectively. Lastly, we demonstrate that planar graphene-based van der Waals heterostructures behave effectively as supermetals, exhibiting reflective properties that surpass the reflectivity of gold and silver that are currently considered the state-of-the-art materials for mirroring applications in space applications. The (meta)materials we introduce exhibit an order-of-magnitude lower mass density, making them suitable candidates for future light-sail technologies intended for space exploration.
", "doi": "10.7907/Z97H1GS1", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:11022", "collection": "thesis", "collection_id": "11022", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042018-194533722", "primary_object_url": { "basename": "phd-thesis_June2018.pdf", "content": "final", "filesize": 71599010, "license": "cc_by_nc", "mime_type": "application/pdf", "url": "/11022/1/phd-thesis_June2018.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Silicon Integrated Arrays: From Microwave to IR", "author": [ { "family_name": "Abiri", "given_name": "Behrooz", "orcid": "0000-0002-3317-2752", "clpid": "Abiri-Behrooz" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Integrated chips have enabled realization and mass production of complex systems in a small form factor. Through process miniaturization many novel applications in silicon photonics and electronic systems have been enabled. In this thesis I have provided several examples of innovations that are only enabled by integration. I have also demonstrated how electronics and photonics circuits can complement each other to achieve a system with superior performance.
", "doi": "10.7907/MNYK-Y158", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10196", "collection": "thesis", "collection_id": "10196", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05232017-161027761", "primary_object_url": { "basename": "thesis-submit.pdf", "content": "final", "filesize": 10069890, "license": "other", "mime_type": "application/pdf", "url": "/10196/1/thesis-submit.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Physics and Applications of Microresonator Solitons and Electro-optic Frequency Combs", "author": [ { "family_name": "Yi", "given_name": "Xu", "orcid": "0000-0002-2485-1104", "clpid": "Yi-Xu" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Beichman", "given_name": "Charles A.", "orcid": "0000-0002-5627-5471", "clpid": "Beichman-C-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Frequency combs are having a broad impact on science and technology because they provide a way to coherently link radio/microwave-rate electrical signals with optical-rate signals derived from lasers and atomic transitions. A new, miniature realization, the microcomb, that uses chip-based microresonators can potentially revolutionize instrumentation, time keeping, spectroscopy, and navigation. Microcombs were first demonstrated using a form of cascaded four-wave mixing. However, the recent discovery of dissipative soliton microcombs enables phase-locked spectra with reproducible envelopes, as required in many frequency comb applications. In addition, these solitons are confined in a high-Q microresonator, thereby creating a rich landscape for research in nonlinear optical phenomena. In this thesis, these solitons are demonstrated for the first time in a silica microcavity. Significantly, the device provides a microwave-detectable soliton repetition rate, which is essential to many comb applications. The unusual properties of the solitons are studied from a theoretical viewpoint using a Lagrangian formalism and predictions of the theory are confirmed experimentally. In the course of this work, a new optical soliton, the Stokes soliton, was also discovered. In addition to soliton mode locking, another novel and compact platform, the electro-optical modulation frequency comb, was studied. This type of frequency comb was used to demonstrate a novel electro-optic form of frequency division for stable microwave synthesis. It was also modified to perform astronomical calibration for exoplanet detection at the Keck Observatory in Hawaii.
", "doi": "10.7907/Z9FT8J22", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10002", "collection": "thesis", "collection_id": "10002", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01032017-032640614", "primary_object_url": { "basename": "20170212-optics-high-efficiency.pdf", "content": "final", "filesize": 6609982, "license": "other", "mime_type": "application/pdf", "url": "/10002/67/20170212-optics-high-efficiency.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Optics for High-Efficiency Full Spectrum Photovoltaics", "author": [ { "family_name": "Darbe", "given_name": "Sunita", "orcid": "0000-0002-8099-1814", "clpid": "Darbe-Sunita" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Greer", "given_name": "Julia R.", "clpid": "Greer-J-R" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "While the price of solar energy has dropped dramatically in the last few years, costs must be further reduced to reach wide-scale adoption. One strategy to decrease cost is to increase efficiency. Photovoltaic energy conversion is most efficient for a narrow frequency range. Lack of absorption of low energy photons and thermalization of high-energy photons leads lead to a loss of over 40% of incident solar power on a silicon cell. Current-matching and lattice-matching restrictions limit the efficiency of traditional monolithic multijunction solar cells. In order to avoid these limitations and realize ultrahigh efficiency (close to 50%), this thesis explores use of optical elements to split broadband sunlight into multiple spectral bands that can each be sent to physically separated solar cells tuned to best convert that band.
\r\n\r\nDesign of a holographic diffraction grating based spectrum-splitting system resulted in a simulated module efficiency of 37%, meeting the efficiency of state-of-the-art modules. One of four holographic grating stacks is experimentally characterized. Next, a design incorporating dichroic filters, seven subcells with bandgaps spanning the solar spectrum, and concentrators with efficiency potential exceeding 45% module efficiency is presented. While prototyping this design, we also used on-going cost-modeling to ensure that our design was on-track to be a high-volume technology with low lifetime energy cost.
\r\n\r\nFinally, high-contrast gratings are used as resonant, dielectric spectrally selective mirrors in a tandem luminescent solar concentrator and as alternatives to Bragg reflectors. Gratings can have omnidirectional, high reflectivity by appropriately offsetting grating resonances in nano-patterned subwavelength thickness high-refractive index material. Subwavelength feature sizes suppress diffraction, and the high-refractive index of the grating layer leads to relatively angle-insensitive reflectance. Gratings can be fabricated by nanoimprint lithography, making them a scalable and economical option for photovoltaic applications. Simulations show hemispherically average reflectivity near 90% possible from a single subwavelength thickness layer. These properties are well suited for a variety of applications including multiple spectrum-splitting device architectures.
", "doi": "10.7907/Z96W9833", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10096", "collection": "thesis", "collection_id": "10096", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03152017-114949088", "primary_object_url": { "basename": "Miyazono_Evan_2017.pdf", "content": "final", "filesize": 31648083, "license": "cc_by_nc_sa", "mime_type": "application/pdf", "url": "/10096/1/Miyazono_Evan_2017.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Nanophotonic Resonators for Optical Quantum Memories based on Rare-Earth-Doped Materials", "author": [ { "family_name": "Miyazono", "given_name": "Evan Tsugio", "orcid": "0000-0003-2176-0335", "clpid": "Miyazono-Evan-Tsugio" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The growing interest in optical quantum systems has led to the exploration of multiple platforms. Though pioneering experiments were performed in trapped atom and trapped ion systems, solid state systems show promise of being scalable and robust. Rare earth dopants in crystalline hosts are an appealing option because they possess a rich spectrum of energy levels that result from a partially filled electron orbital. While level structure varies across the period, all elements possess crystal field splittings corresponding to near infra-red or optical frequencies, as well as Zeeman and often hyperfine levels separated by radio frequency and microwave frequencies. These levels demonstrate long excited-state lifetimes and coherence times and have been used in diverse applications, including demonstrating storage of a photonic state, converting of optical to microwave photons, and manipulating a single ion as a single qubit. The ions' weak interaction with their environment results in low coupling to optical fields, which had previously required measurements with macroscopically large ensembles of ions. Coupling the ions to an optical cavity enables the use of a smaller ensemble, which is required for the development of the aforementioned technologies in an on-chip scalable architecture.
\r\n\r\nThis thesis contains recent progress towards fabricating optical micro and nanocavities coupled to ensembles of erbium ions, mainly erbium in yttrium orthosilicate. In one design, focused ion beam milling was used to create a triangular nanobeam photonic crystal cavity in a bulk erbium-doped substrate. A second design leveraged the fabrication capabilities of silicon photonics, defining amorphous silicon ring resonators using electron beam lithography and dry etching. These devices coupled evanescently to erbium ions below the ring, in the bulk substrate. Simulation, design, fabrication, and characterization of both resonators are discussed. Coupling between the ions and the resonator is demonstrated for each, and capabilities offered by these devices are described. Preliminary work implementing coherent control of erbium ions is presented. Lastly, alternative substrates are evaluated for possible future solid-state erbium systems.
", "doi": "10.7907/Z98K773F", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10313", "collection": "thesis", "collection_id": "10313", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06082017-062231802", "type": "thesis", "title": "Atom-Light Interactions in a Photonic Crystal Waveguide", "author": [ { "family_name": "Hood", "given_name": "Jonathan David", "orcid": "0000-0001-7566-4475", "clpid": "Hood-Jonathan-David" } ], "thesis_advisor": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" } ], "thesis_committee": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Brandao", "given_name": "Fernando", "orcid": "0000-0003-3866-9378", "clpid": "Brand\u00e3o-F-G-S-L" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_pma" } ], "abstract": "New opportunities for optical physics emerge from the integration of cold atoms with nanophotonic devices. Due to their small optical loss and tight field confinement, these nanoscale dielectric devices are capable of mediating strong atom-light interactions and open new avenues for quantum transport and quantum many-body phenomena. In particular, coupling atoms to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for generating tunable range coherent atom-atom interactions which are mediated by the guided mode photons.", "doi": "10.7907/Z9NV9G9Z", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10313", "collection": "thesis", "collection_id": "10313", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06082017-062231802", "type": "thesis", "title": "Atom-Light Interactions in a Photonic Crystal Waveguide", "author": [ { "family_name": "Hood", "given_name": "Jonathan David", "orcid": "0000-0001-7566-4475", "clpid": "Hood-Jonathan-David" } ], "thesis_advisor": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" } ], "thesis_committee": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Brandao", "given_name": "Fernando", "orcid": "0000-0003-3866-9378", "clpid": "Brand\u00e3o-F-G-S-L" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_pma" } ], "abstract": "New opportunities for optical physics emerge from the integration of cold atoms with nanophotonic devices. Due to their small optical loss and tight field confinement, these nanoscale dielectric devices are capable of mediating strong atom-light interactions and open new avenues for quantum transport and quantum many-body phenomena. In particular, coupling atoms to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for generating tunable range coherent atom-atom interactions which are mediated by the guided mode photons.", "doi": "10.7907/Z9NV9G9Z", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10255", "collection": "thesis", "collection_id": "10255", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022017-134307910", "primary_object_url": { "basename": "Thesis_Su-Peng_Yu_v1.61_final_Defended_26-MAY-17.pdf", "content": "final", "filesize": 29037638, "license": "other", "mime_type": "application/pdf", "url": "/10255/1/Thesis_Su-Peng_Yu_v1.61_final_Defended_26-MAY-17.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Nano-Photonic Platform for Atom-Light Interaction", "author": [ { "family_name": "Yu", "given_name": "Su-Peng", "orcid": "0000-0003-1348-7447", "clpid": "Yu-Su-Peng" } ], "thesis_advisor": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" } ], "thesis_committee": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Chen", "given_name": "Xie", "orcid": "0000-0003-2215-2497", "clpid": "Chen-Xie" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_pma" } ], "abstract": "Development of technology can allow access to new regimes in science and creation of new fields of research. The development of ultra-high finesse mirror technology enabled the development of the field of cavity quantum electrodynamics, and an abundance of wonderful physics experiments soon followed. The sophistication of the field of nano-fabrication and nano-photonics would allow unprecedented capability to mold the shape and flow of light, and provide a novel platform for efficient and hopefully integrable quantum systems. In this project, we hope to interface cold atoms, perhaps the most quintessential of quantum systems, to the engineering power of nano-photonics. We believe this field of study will not only lead to the demonstration of new physics in the quantum regime, but work toward building a network with quantum capabilities mediated by optical channels.
\r\n\r\nIn this project, we develop a nano-fabricated platform capable of interfacing nano-photonic devices with cold Cesium atoms in free-space. Nano-photonic waveguide devices are fabricated in a Silicon Nitride device layer on Silicon substrate. The fabrication is compatible with conventional semiconductor fabrication processes, and the chip design has been adapted to allow incorporation with free-space optics to support cold Cesium atom cloud around the waveguides. An ultra-high vacuum system that is compatible to the chip and its supporting structures was constructed to perform experiments.
\r\n\r\nWith our system, we were able to fabricate and characterize nano-photonic structures, including 1D photonic crystal waveguides, cavities, and 2D photonic crystal slabs. For the 1D photonic crystal waveguide devices, enhanced atom-light coupling between localized Cesium atoms in the vicinity of the devices, and also atom-atom interaction between Cesium atoms mediated by the guided mode of the photonic crystal waveguide, has been observed. The 2D photonic devices allow us many capabilities beyond that of the 1D waveguide. Demonstration of exotic optical properties including natural decay rate suppression and circular polarization engineering, should be within reach in the near future.
", "doi": "10.7907/Z9668B7F", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10255", "collection": "thesis", "collection_id": "10255", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022017-134307910", "primary_object_url": { "basename": "Thesis_Su-Peng_Yu_v1.61_final_Defended_26-MAY-17.pdf", "content": "final", "filesize": 29037638, "license": "other", "mime_type": "application/pdf", "url": "/10255/1/Thesis_Su-Peng_Yu_v1.61_final_Defended_26-MAY-17.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Nano-Photonic Platform for Atom-Light Interaction", "author": [ { "family_name": "Yu", "given_name": "Su-Peng", "orcid": "0000-0003-1348-7447", "clpid": "Yu-Su-Peng" } ], "thesis_advisor": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" } ], "thesis_committee": [ { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Chen", "given_name": "Xie", "orcid": "0000-0003-2215-2497", "clpid": "Chen-Xie" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_pma" } ], "abstract": "Development of technology can allow access to new regimes in science and creation of new fields of research. The development of ultra-high finesse mirror technology enabled the development of the field of cavity quantum electrodynamics, and an abundance of wonderful physics experiments soon followed. The sophistication of the field of nano-fabrication and nano-photonics would allow unprecedented capability to mold the shape and flow of light, and provide a novel platform for efficient and hopefully integrable quantum systems. In this project, we hope to interface cold atoms, perhaps the most quintessential of quantum systems, to the engineering power of nano-photonics. We believe this field of study will not only lead to the demonstration of new physics in the quantum regime, but work toward building a network with quantum capabilities mediated by optical channels.
\r\n\r\nIn this project, we develop a nano-fabricated platform capable of interfacing nano-photonic devices with cold Cesium atoms in free-space. Nano-photonic waveguide devices are fabricated in a Silicon Nitride device layer on Silicon substrate. The fabrication is compatible with conventional semiconductor fabrication processes, and the chip design has been adapted to allow incorporation with free-space optics to support cold Cesium atom cloud around the waveguides. An ultra-high vacuum system that is compatible to the chip and its supporting structures was constructed to perform experiments.
\r\n\r\nWith our system, we were able to fabricate and characterize nano-photonic structures, including 1D photonic crystal waveguides, cavities, and 2D photonic crystal slabs. For the 1D photonic crystal waveguide devices, enhanced atom-light coupling between localized Cesium atoms in the vicinity of the devices, and also atom-atom interaction between Cesium atoms mediated by the guided mode of the photonic crystal waveguide, has been observed. The 2D photonic devices allow us many capabilities beyond that of the 1D waveguide. Demonstration of exotic optical properties including natural decay rate suppression and circular polarization engineering, should be within reach in the near future.
", "doi": "10.7907/Z9668B7F", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10247", "collection": "thesis", "collection_id": "10247", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012017-163114372", "type": "thesis", "title": "Nonlinear Optics in Chip-based Microresonators and their Applications", "author": [ { "family_name": "Suh", "given_name": "Myoung-Gyun", "orcid": "0000-0002-9527-0585", "clpid": "Suh-Myoung-Gyun" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Optical micro-resonators have been studied for decades as a platform to investigate optical physics, and to miniaturize bulky optical systems. In the last decade, optical frequency combs, which have revolutionized the precision measurement of time and frequency, have been demonstrated in optical micro-resonators via the combined effect of parametric oscillation and cascaded four-wave mixing. More recently, soliton mode-locking has made possible low-noise/reproducible generation of these miniature combs (microcombs). In this thesis, we demonstrated the generation of soliton microcombs from silica wedge disk micro-resonators and the characteristics of the soliton microcombs are described. We also applied soliton microcombs to dual-comb spectroscopy and distance measurement (LIDAR) for the first time. Also, ways to improve spectral resolution, signal-to-noise ratio, and spectral coverage are discussed. In addition to soliton microcombs, a novel spiral resonator is studied as a stable optical frequency reference. Combined with a frequency comb, this new type of chip-based reference cavity is also applied to generate stable microwaves via optical frequency division. Lastly, we generated a stimulated Brillouin laser (SBL) from the optical micro-resonator and its phonon-limited linewidth is studied. Application of the SBL for rotation measurement is also demonstrated. This thesis is organized into six chapters. Throughout the thesis, the implication and potential of my PhD work toward chip-based advanced optics system are discussed.
", "doi": "10.7907/Z92F7KG8", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9943", "collection": "thesis", "collection_id": "9943", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10182016-152744850", "primary_object_url": { "basename": "thesis_CULei.pdf", "content": "final", "filesize": 44850600, "license": "other", "mime_type": "application/pdf", "url": "/9943/1/thesis_CULei.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Circuit Cavity Electromechanics in the Quantum Regime", "author": [ { "family_name": "Lei", "given_name": "Chan U", "orcid": "0000-0002-2790-2421", "clpid": "Lei-Chan-U" } ], "thesis_advisor": [ { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" } ], "thesis_committee": [ { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Chen", "given_name": "Yanbei", "clpid": "Chen-Yanbei" }, { "family_name": "Adhikari", "given_name": "Rana", "clpid": "Adhikari-R" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_pma" } ], "abstract": "Generating nonclassical states of a macroscopic mechanical object has been a subject of considerable interest. It offers a route toward fundamental test of quantum mechanics in an unexplored regime. However, a macroscopic quantum state is very susceptible to decoherence due to the environment. One way to generate robust quantum states is quantum reservoir engineering. In this work, we utilize the reservoir engineering scheme to generate a steady quantum squeezed state of a micron-scale mechanical oscillator in an electromechanical system. Together with the backaction evading measurement technique, we demonstrate a quantum nondemolition measurement of the mechanical quadratures to characterize the quantum squeezed state. By measuring the quadrature variances of the mechanical motion, more than 3dB squeezing below the zero-point level has been achieved.", "doi": "10.7907/Z93T9F6W", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9989", "collection": "thesis", "collection_id": "9989", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12012016-194127904", "type": "thesis", "title": "An Optofluidic Ring Resonator Platform for Rapid and Robust Sensing", "author": [ { "family_name": "Popescu", "given_name": "Paula Flor", "clpid": "Popescu-Paula-Flor" } ], "thesis_advisor": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Ring resonators show great potential as sensitive optical detectors for studies of biomolecular interactions, drug screening, and point-of-care diagnostics. They are sensitive to minute changes in the refractive index of the surrounding medium, which enables them to detect and quantify sub-femtomolar concentrations of target molecules. This thesis investigates the advantages of an optofluidic ring resonator platform that employs a differential measurement scheme for reducing environmental noise due to temperature and pressure fluctuations. Through simulations and experiments, I determine the sensitivity of the platform to changes in the target analyte concentration and to environmental noise, and demonstrate the benefits of employing a second, reference, ring resonator.
\r\n\r\nA crucial step in achieving versatile biosensing platforms is the integration of the high sensitivity resonators into platforms with short assay times and robust chemical functionalization. I focus on the development of robust chemistry protocols for depositing linker silane layers for biomolecular interaction studies. Moreover, since the fluid handling scheme strongly influences the response time of the platform, I design and test two fluidic platforms integrated with elastomeric valves that show excellent response times. To further increase the response time of the sensing platform, I explore the effects of a patterned channel geometry on the enhancement of mass transport to the sensor in low Reynolds number flows.
", "doi": "10.7907/Z9H41PFQ", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10014", "collection": "thesis", "collection_id": "10014", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01172017-145551495", "type": "thesis", "title": "Theoretical and Experimental Investigation of Phonon Boundary Scattering in Thin Silicon Membranes", "author": [ { "family_name": "Ravichandran", "given_name": "Navaneetha Krishnan", "clpid": "Ravichandran-Navaneetha-Krishnan" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" } ], "thesis_committee": [ { "family_name": "Hunt", "given_name": "Melany L.", "clpid": "Hunt-M-L" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" }, { "family_name": "Blanquart", "given_name": "Guillaume", "clpid": "Blanquart-G" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Resnick Sustainability Institute" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The thermal transport properties of thin semiconductor membranes play an important role in the performance of many technologies like micro-electronics and solid-state energy conversion. The dominant resistance to heat flow in thin membranes is offered by the scattering of thermal phonons at the membrane boundaries. In this dissertation, we examine the nature of microscopic phonon boundary scattering processes and their effect on the thermal conductivity of the thin membranes using a pump-probe experimental technique and computationally efficient solutions of the phonon Boltzmann transport equation (BTE).
\r\n\r\nFirst, we investigate the boundary scattering-limited thermal transport in nanostructures using an efficient variance-reduced Monte Carlo (MC) solution of the BTE to elucidate the impact of specular and diffuse phonon boundary scattering events on the thermal conductivity of the nanostructures. To directly measure the relative frequency of these two boundary scattering events, called the phonon specularity parameter, we design, implement and characterize a non-contact laser-based pump-probe experiment called the transient grating (TG) to perform phonon mode-dependent measurements of the specularity parameter in suspended free-standing thin silicon membranes. We describe the phenomenon of quasiballistic heat conduction, which enables the phonon mode-dependent measurements of the specularity parameter, and derive a transfer function based on the BTE with ab-initio phonon properties as inputs, to connect the specularity parameter with the experimentally measured thermal conductivity of the thin membranes.
\r\n\r\nFinally, we present the methodology adopted to invert the BTE transfer function to extract the phonon specularity parameter from the thermal conductivity measurements in the TG experiment, while rigorously accounting for the experimental uncertainties. We find that the observed magnitudes and trends of the thermal conductivity of the thin membranes cannot be explained by the 50-year old Ziman's model for the phonon specularity parameter and the Fuchs-Sondheimer theory of phonon boundary scattering. We also find that the partially specular boundary scattering picture of phonon boundary interactions works well for one of the membranes, enabling a direct measurement of the mode-dependent phonon specularity parameter for the first time in an experiment. We discuss the possibility of phonon mode conversion at the boundaries of a few membranes for which the partially specular phonon boundary scattering picture fails to explain the observed thermal conductivity trends. Considering the importance of understanding phonon boundary scattering to engineer and improve nanoscale device performance, we expect that the new experimental and computational tools developed in this work will advance a variety of nanoscale energy applications and further our understanding of nanoscale heat transport.
", "doi": "10.7907/Z9SJ1HK2", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10006", "collection": "thesis", "collection_id": "10006", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01062017-221235563", "type": "thesis", "title": "Nanoscale Thermal Transport with Photons and Phonons", "author": [ { "family_name": "Ding", "given_name": "Ding", "clpid": "Ding-Ding" } ], "thesis_advisor": [ { "family_name": "Minnich", "given_name": "Austin", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Fultz", "given_name": "Brent T.", "orcid": "0000-0002-6364-8782", "clpid": "Fultz-B-T" }, { "family_name": "Bernardi", "given_name": "Marco", "orcid": "0000-0001-7289-9666", "clpid": "Bernardi-Marco" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Minnich", "given_name": "Austin J.", "orcid": "0000-0002-9671-9540", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Recent progress in nanosciences challenges the conventional understanding of Fourier's law for heat conduction and Planck's law for thermal radiation, calling for theoretical and experimental advancement to improve our understanding at these length scales. Advances in both theoretical and experimental progress at these length scale have been made in the past two decades, but there are still many challenges and possibilities in further understanding how heat conducts or radiates at these length scales.
\r\n\r\nThe first half of this thesis focuses on topics in nanoscale thermal radiation. First, we will discuss an effort to modify thermal emission using a hyperbolic metamaterial (HMM). Recent efforts in utilizing different metamaterial designs to modify thermal emission has led to greater control over the spectral and directional properties of thermal radiation, and the HMM is one such metamaterial. HMM is typically made up of sub-wavelength alternating layers of metal and dielectric that result in an anisotropic permittivity. Here we demonstrate that an annular, transparent HMM lens enables selective controlling of the plasmonic resonance such that a nanowire emitter, surrounded by an HMM, appears dark to incoming radiation from an adjacent nanowire emitter unless the second emitter is surrounded by an identical lens.
\r\n\r\nWhile many metamaterial schemes exist to modify thermal emission, these schemes are ultimately limited by the maximum possible emission of a blackbody. In an effort to further increase radiative thermal emission, we made another effort to explore the possibility of removing the enhanced but trapped thermal radiation energy density at sub-wavelength distances. Here, we propose and numerically demonstrate an active scheme that exploits the monochromatic nature of near-field thermal radiation to drive a transition in a laser gain medium, which, when coupled with external optical pumping, allows the resonant surface mode to be emitted into the far-field. We compare this proposed active radiative cooling (ARC) approach to the better-understood laser cooling of solids (LCS) technique, which achieves cooling by extracting phonons instead of thermal radiation. We show that LCS and ARC can be described with the same mathematical formalism and find that ARC can achieve higher efficiency and extracted power over a wide range of conditions.
\r\n\r\nIn the second half of thesis, we switch our attention to nanoscale heat conduction where phonons are the dominant heat carriers. Phonons require a medium to travel, unlike thermal radiation, and thus experience much stronger interaction with the medium. Typical assumptions of many scattering events of phonons at the larger length scales break down at the nanoscale when phonon transport can no longer be accurately described by diffusion theory. Here, we present a numerical modeling effort using the Boltzmann Transport Equation to accurately model nanoscale phonon transport of a recent experiment. We show a calculated trend of pump beam size dependence on thermal conductivity similar to results from the time-domain thermal reflectance (TDTR) experiment. We also identify the radial suppression function that describes the suppression in heat flux, compared to Fourier's law, that occurs due to quasiballistic transport and demonstrate good agreement with experimental data.
\r\n\r\nWhile time-domain thermal reflectance (TDTR) experiment is widely used to characterize thermal transport, it is not ideal for in-plane thermal measurements compared to the transient grating (TG) techniques which utilize interference of two beams to create a in-plane grating pattern for thermal measurements. In the last part of my thesis, we highlight details of an experimental effort to develop the ultra-fast transient grating (TG) technique capable of measuring fast thermal decays. We will then highlight the results of thermal and acoustic measurements of molybdenum disulphide that can be obtained from this technique. Our results are in good agreement with other measurements and calculations.
\r\n\r\nWith nanosciences paving way for the future of technology, understanding thermal management at the nanoscale is crucial for device performance and reducing energy waste. We believe that these results in thermal radiation and conduction will benefit thermal management at the nanoscale.
\r\n", "doi": "10.7907/Z94Q7RZ0", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:9781", "collection": "thesis", "collection_id": "9781", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05272016-075803376", "type": "thesis", "title": "Optomechanics with Superfluid Helium-4", "author": [ { "family_name": "De Lorenzo", "given_name": "Laura Anne", "clpid": "Delorenzo-Laura-Anne" } ], "thesis_advisor": [ { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" } ], "thesis_committee": [ { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" }, { "family_name": "Chen", "given_name": "Yanbei", "clpid": "Chen-Yanbei" }, { "family_name": "Adhikari", "given_name": "Rana", "clpid": "Adhikari-R" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_eng" } ], "abstract": "We demonstrate the utility of superfluid helium-4 as an extremely low loss optomechanical element. We form an optomechanical system with a cylindrical niobium superconducting TE011 resonator whose 40 cm3 inner cylindrical cavity is filled with 4He. [1] Coupling is realized via the variations in permittivity resulting from the density profile of the acoustic modes. Acoustic losses in helium-4 below 500 mK are governed by the intrinsic nonlinearity of sound, leading to an attenuation which drops as T 4, indicating the possibility of quality factors (Q) over 1010 at 10 mK. In our lowest loss mode, we demonstrate this T 4 law down to 50 mK, realizing an acoustic Q of 1.35·108 at 8.1 kHz. When coupled with a low phase noise microwave source, we expect this system to be utilized as a probe of macroscopic quantized motion, for precision measurements to search for fundamental physical length scales, and as a continuous gravitational wave detector. Our estimates suggest that a resonant superfluid acoustic system could exceed the sensitivity of current broad-band detectors for narrow-band sources such as pulsars [2].", "doi": "10.7907/Z9RJ4GD7", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9684", "collection": "thesis", "collection_id": "9684", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04242016-093536420", "primary_object_url": { "basename": "Brown_Ana_2016.pdf", "content": "final", "filesize": 5129731, "license": "other", "mime_type": "application/pdf", "url": "/9684/1/Brown_Ana_2016.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Classical and Quantum Effects in Plasmonic Metals", "author": [ { "family_name": "Brown", "given_name": "Ana Maii", "orcid": "0000-0003-3008-2310", "clpid": "Brown-Ana-Maii" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The field of plasmonics exploits the unique optical properties of metallic nanostructures to concentrate and manipulate light at subwavelength length scales. Metallic nanostructures get their unique properties from their ability to support surface plasmons\u2013 coherent wave-like oscillations of the free electrons at the interface between a conductive and dielectric medium. Recent advancements in the ability to fabricate metallic nanostructures with subwavelength length scales have created new possibilities in technology and research in a broad range of applications.
\r\n\r\nIn the first part of this thesis, we present two investigations of the relationship between the charge state and optical state of plasmonic metal nanoparticles. Using experimental bias-dependent extinction measurements, we derive a potential- dependent dielectric function for Au nanoparticles that accounts for changes in the physical properties due to an applied bias that contribute to the optical extinction. We also present theory and experiment for the reverse effect\u2013 the manipulation of the carrier density of Au nanoparticles via controlled optical excitation. This plasmoelectric effect takes advantage of the strong resonant properties of plasmonic materials and the relationship between charge state and optical properties to eluci- date a new avenue for conversion of optical power to electrical potential.
\r\n\r\nThe second topic of this thesis is the non-radiative decay of plasmons to a hot-carrier distribution, and the distribution\u2019s subsequent relaxation. We present first-principles calculations that capture all of the significant microscopic mechanisms underlying surface plasmon decay and predict the initial excited carrier distributions so generated. We also preform ab initio calculations of the electron-temperature dependent heat capacities and electron-phonon coupling coefficients of plasmonic metals. We extend these first-principle methods to calculate the electron-temperature dependent dielectric response of hot electrons in plasmonic metals, including direct interband and phonon-assisted intraband transitions. Finally, we combine these first-principles calculations of carrier dynamics and optical response to produce a complete theoretical description of ultrafast pump-probe measurements, free of any fitting parameters that are typical in previous analyses.
", "doi": "10.7907/Z9QV3JHT", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9292", "collection": "thesis", "collection_id": "9292", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11242015-234332347", "primary_object_url": { "basename": "Thesis Carissa Nicole Eisler.pdf", "content": "final", "filesize": 439845948, "license": "other", "mime_type": "application/pdf", "url": "/9292/1/Thesis Carissa Nicole Eisler.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Photonic and Device Design Principles for Ultrahigh-Efficiency (>50%), Spectrum-Splitting Photovoltaics", "author": [ { "family_name": "Eisler", "given_name": "Carissa Nicole", "orcid": "0000-0002-5755-5280", "clpid": "Eisler-Carissa-Nicole" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Flagan", "given_name": "Richard C.", "clpid": "Flagan-R-C" }, { "family_name": "Kornfield", "given_name": "Julia A.", "clpid": "Kornfield-J-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The sun has the potential to power the Earth's total energy needs, but electricity from solar power still constitutes an extremely small fraction of our power generation because of its high cost relative to traditional energy sources. Therefore, the cost of solar must be reduced to realize a more sustainable future. This can be achieved by significantly increasing the efficiency of modules that convert solar radiation to electricity. In this thesis, we consider several strategies to improve the device and photonic design of solar modules to achieve record, ultrahigh (> 50%) solar module efficiencies. First, we investigate the potential of a new passivation treatment, trioctylphosphine sulfide, to increase the performance of small GaAs solar cells for cheaper and more durable modules. We show that small cells (mm2), which currently have a significant efficiency decrease (~ 5%) compared to larger cells (cm2) because small cells have a higher fraction of recombination-active surface from the sidewalls, can achieve significantly higher efficiencies with effective passivation of the sidewalls. We experimentally validate the passivation qualities of treatment by trioctylphosphine sulfide (TOP:S) through four independent studies and show that this facile treatment can enable efficient small devices. Then, we discuss our efforts toward the design and prototyping of a spectrum-splitting module that employs optical elements to divide the incident spectrum into different color bands, which allows for higher efficiencies than traditional methods. We present a design, the polyhedral specular reflector, that has the potential for > 50% module efficiencies even with realistic losses from combined optics, cell, and electrical models. Prototyping efforts of one of these designs using glass concentrators yields an optical module whose combined spectrum-splitting and concentration should correspond to a record module efficiency of 42%. Finally, we consider how the manipulation of radiatively emitted photons from subcells in multijunction architectures can be used to achieve even higher efficiencies than previously thought, inspiring both optimization of incident and radiatively emitted photons for future high efficiency designs. In this thesis work, we explore novel device and photonic designs that represent a significant departure from current solar cell manufacturing techniques and ultimately show the potential for much higher solar cell efficiencies. ", "doi": "10.7907/Z9PN93HB", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9532", "collection": "thesis", "collection_id": "9532", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01122016-170853872", "primary_object_url": { "basename": "Tim_Thesis.pdf", "content": "final", "filesize": 146422428, "license": "other", "mime_type": "application/pdf", "url": "/9532/1/Tim_Thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optomechanical Inertial Sensors and Feedback Cooling", "author": [ { "family_name": "Blasius", "given_name": "Timothy Dobson", "clpid": "Blasius-Timothy-Dobson" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Adhikari", "given_name": "Rana", "clpid": "Adhikari-R" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_pma" } ], "abstract": "The optomechanical interaction is an extremely powerful tool with which to measure mechanical motion. The displacement resolution of chip-scale optomechanical systems has been measured on the order of 1⁄10th of a proton radius. So strong is this optomechanical interaction that it has recently been used to remove almost all thermal noise from a mechanical resonator and observe its quantum ground-state of motion starting from cryogenic temperatures.
\r\n\r\nIn this work, chapter 1 describes the basic physics of the canonical optomechanical system, optical measurement techniques, and how the optomechanical interaction affects the coupled mechanical resonator. In chapter 2, we describe our techniques for realizing this canonical optomechanical system in a chip-scale form factor.
\r\n\r\nIn chapter 3, we describe an experiment where we used radiation pressure feedback to cool a mesoscopic mechanical resonator near its quantum ground-state from room-temperature. We cooled the resonator from a room temperature phonon occupation of <n> = 6.5 million to an occupation of <n> = 66, which means the resonator is in its ground state approximately 2% of the time, while being coupled to a room-temperature thermal environment. At the time of this work, this is the closest a mesoscopic mechanical resonator has been to its ground-state of motion at room temperature, and this work begins to open the door to room-temperature quantum control of mechanical objects.
\r\n\r\nChapter 4 begins with the realization that the displacement resolutions achieved by optomechanical systems can surpass those of conventional MEMS sensors by an order of magnitude or more. This provides the motivation to develop and calibrate an optomechanical accelerometer with a resolution of approximately 10 micro-g/rt-Hz over a bandwidth of approximately 30 kHz. In chapter 5, we improve upon the performance and practicality of this sensor by greatly increasing the test mass size, investigating and reducing low-frequency noise, and incorporating more robust optical coupling techniques and capacitive wavelength tuning. Finally, in chapter 6 we present our progress towards developing another optomechanical inertial sensor - a gyroscope.
\r\n", "doi": "10.7907/Z9NK3BZS", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:8754", "collection": "thesis", "collection_id": "8754", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01162015-120819334", "primary_object_url": { "basename": "AlexKrause_Thesis_2015_final.pdf", "content": "final", "filesize": 72074881, "license": "other", "mime_type": "application/pdf", "url": "/8754/8/AlexKrause_Thesis_2015_final.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Acceleration Sensing, Feedback Cooling, and Nonlinear Dynamics with Nanoscale Cavity-Optomechanical Devices", "author": [ { "family_name": "Krause", "given_name": "Alexander Grey", "clpid": "Krause-Alexander-Grey" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Chen", "given_name": "Yanbei", "clpid": "Chen-Yanbei" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_eng" } ], "abstract": "Light has long been used for the precise measurement of moving bodies, but the burgeoning field of optomechanics is concerned with the interaction of light and matter in a regime where the typically weak radiation pressure force of light is able to push back on the moving object. This field began with the realization in the late 1960's that the momentum imparted by a recoiling photon on a mirror would place fundamental limits on the smallest measurable displacement of that mirror. This coupling between the frequency of light and the motion of a mechanical object does much more than simply add noise, however. It has been used to cool objects to their quantum ground state, demonstrate electromagnetically-induced-transparency, and modify the damping and spring constant of the resonator. Amazingly, these radiation pressure effects have now been demonstrated in systems ranging 18 orders of magnitude in mass (kg to fg).
\r\n\r\nIn this work we will focus on three diverse experiments in three different optomechanical devices which span the fields of inertial sensors, closed-loop feedback, and nonlinear dynamics. The mechanical elements presented cover 6 orders of magnitude in mass (ng to fg), but they all employ nano-scale photonic crystals to trap light and resonantly enhance the light-matter interaction. In the first experiment we take advantage of the sub-femtometer displacement resolution of our photonic crystals to demonstrate a sensitive chip-scale optical accelerometer with a kHz-frequency mechanical resonator. This sensor has a noise density of approximately 10 micro-g/rt-Hz over a useable bandwidth of approximately 20 kHz and we demonstrate at least 50 dB of linear dynamic sensor range. We also discuss methods to further improve performance of this device by a factor of 10.
\r\n\r\nIn the second experiment, we used a closed-loop measurement and feedback system to damp and cool a room-temperature MHz-frequency mechanical oscillator from a phonon occupation of 6.5 million down to just 66. At the time of the experiment, this represented a world-record result for the laser cooling of a macroscopic mechanical element without the aid of cryogenic pre-cooling. Furthermore, this closed-loop damping yields a high-resolution force sensor with a practical bandwidth of 200 kHZ and the method has applications to other optomechanical sensors.
\r\n\r\nThe final experiment contains results from a GHz-frequency mechanical resonator in a regime where the nonlinearity of the radiation-pressure interaction dominates the system dynamics. In this device we show self-oscillations of the mechanical element that are driven by multi-photon-phonon scattering. Control of the system allows us to initialize the mechanical oscillator into a stable high-amplitude attractor which would otherwise be inaccessible. To provide context, we begin this work by first presenting an intuitive overview of optomechanical systems and then providing an extended discussion of the principles underlying the design and fabrication of our optomechanical devices.
", "doi": "10.7907/Z98K771J", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8991", "collection": "thesis", "collection_id": "8991", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042015-232226135", "primary_object_url": { "basename": "Thesis_Yaakov_Vilenchik_2015.pdf", "content": "final", "filesize": 2835041, "license": "other", "mime_type": "application/pdf", "url": "/8991/1/Thesis_Yaakov_Vilenchik_2015.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Narrow-Linewidth Si/III-V Lasers: a Study of Laser Dynamics and Nonlinear Effects", "author": [ { "family_name": "Vilenchik", "given_name": "Yaakov", "clpid": "Vilenchik-Yaakov" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Narrow-linewidth lasers play an important role in a wide variety of applications, from sensing and spectroscopy to optical communication and on-chip clocks. Current narrow-linewidth systems are usually implemented in doped fibers and are big, expensive, and power-hungry. Semiconductor lasers compete favorably in size, cost, and power consumption, but their linewidth is historically limited to the sub-MHz regime. However, it has been recently demonstrated that a new design paradigm, in which the optical energy is stored away from the active region in a composite high-Q resonator, has the potential to dramatically improve the coherence of the laser.
\r\n \r\nThis work explores this design paradigm, as applied on the hybrid Si/III-V platform. It demonstrates a record sub-KHz white-noise-floor linewidth. It further shows, both theoretically and experimentally, that this strategy practically eliminates Henry\u2019s linewidth enhancement by positioning a damped relaxation resonance at frequencies as low as 70 MHz, yielding truly quantum limited devices at frequencies of interest.
\r\n\r\nIn addition to this empirical contribution, this work explores the limits of performance of this platform. Here, the effect of two-photon-absorption and free-carrier-absorption are analyzed, using modified rate equations and Langevin force approach. The analysis predicts that as the intra-cavity field intensity builds up in the high-Q resonator, non-linear effects cause a new domain of performance-limiting factors. Steady-state behavior, laser dynamics, and frequency noise performance are examined in the context of this unique platform, pointing at the importance of nonlinear effects.
\r\n\r\nThis work offers a theoretical model predicting laser performance in light of nonlinear effects, obtaining a good agreement with experimental results from fabricated high-Q Si/III-V lasers. In addition to demonstrating unprecedented semiconductor laser performance, this work establishes a first attempt to predict and demonstrate the key impact of nonlinear effects on silicon-based lasers.
", "doi": "10.7907/Z9513W57", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8779", "collection": "thesis", "collection_id": "8779", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03132015-135949868", "primary_object_url": { "basename": "Thesis_SM.pdf", "content": "final", "filesize": 35724427, "license": "other", "mime_type": "application/pdf", "url": "/8779/1/Thesis_SM.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Cavity Optomechanics at Millikelvin Temperatures", "author": [ { "family_name": "Meenehan", "given_name": "Sean Michael", "clpid": "Meenehan-Sean-Michael" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Schwab", "given_name": "Keith C.", "clpid": "Schwab-K-C" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "div_eng" } ], "abstract": "The field of cavity optomechanics, which concerns the coupling of a mechanical object's motion to the electromagnetic field of a high finesse cavity, allows for exquisitely sensitive measurements of mechanical motion, from large-scale gravitational wave detection to microscale accelerometers. Moreover, it provides a potential means to control and engineer the state of a macroscopic mechanical object at the quantum level, provided one can realize sufficiently strong interaction strengths relative to the ambient thermal noise. Recent experiments utilizing the optomechanical interaction to cool mechanical resonators to their motional quantum ground state allow for a variety of quantum engineering applications, including preparation of non-classical mechanical states and coherent optical to microwave conversion. Optomechanical crystals (OMCs), in which bandgaps for both optical and mechanical waves can be introduced through patterning of a material, provide one particularly attractive means for realizing strong interactions between high-frequency mechanical resonators and near-infrared light. Beyond the usual paradigm of cavity optomechanics involving isolated single mechanical elements, OMCs can also be fashioned into planar circuits for photons and phonons, and arrays of optomechanical elements can be interconnected via optical and acoustic waveguides. Such coupled OMC arrays have been proposed as a way to realize quantum optomechanical memories, nanomechanical circuits for continuous variable quantum information processing and phononic quantum networks, and as a platform for engineering and studying quantum many-body physics of optomechanical meta-materials.
\r\n\r\nHowever, while ground state occupancies (that is, average phonon occupancies less than one) have been achieved in OMC cavities utilizing laser cooling techniques, parasitic absorption and the concomitant degradation of the mechanical quality factor fundamentally limit this approach. On the other hand, the high mechanical frequency of these systems allows for the possibility of using a dilution refrigerator to simultaneously achieve low thermal occupancy and long mechanical coherence time by passively cooling the device to the millikelvin regime. This thesis describes efforts to realize the measurement of OMC cavities inside a dilution refrigerator, including the development of fridge-compatible optical coupling schemes and the characterization of the heating dynamics of the mechanical resonator at sub-kelvin temperatures.
\r\n\r\nWe will begin by summarizing the theoretical framework used to describe cavity optomechanical systems, as well as a handful of the quantum applications envisioned for such devices. Then, we will present background on the design of the nanobeam OMC cavities used for this work, along with details of the design and characterization of tapered fiber couplers for optical coupling inside the fridge. Finally, we will present measurements of the devices at fridge base temperatures of Tf = 10 mK, using both heterodyne spectroscopy and time-resolved sideband photon counting, as well as detailed analysis of the prospects for future quantum applications based on the observed optically-induced heating.
", "doi": "10.7907/Z92J68S7", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8677", "collection": "thesis", "collection_id": "8677", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10082014-105407332", "type": "thesis", "title": "Nanophotonic Light Trapping In Thin Solar Cells", "author": [ { "family_name": "Callahan", "given_name": "Dennis Michael", "clpid": "Callahan-Dennis-Michael" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Greer", "given_name": "Julia R.", "clpid": "Greer-J-R" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Over the last several decades there have been significant advances in the study and understanding of light behavior in nanoscale geometries. Entire fields such as those based on photonic crystals, plasmonics and metamaterials have been developed, accelerating the growth of knowledge related to nanoscale light manipulation. Coupled with recent interest in cheap, reliable renewable energy, a new field has blossomed, that of nanophotonic solar cells.
\r\n\r\nIn this thesis, we examine important properties of thin-film solar cells from a nanophotonics perspective. We identify key differences between nanophotonic devices and traditional, thick solar cells. We propose a new way of understanding and describing limits to light trapping and show that certain nanophotonic solar cell designs can have light trapping limits above the so called ray-optic or ergodic limit. We propose that a necessary requisite to exceed the traditional light trapping limit is that the active region of the solar cell must possess a local density of optical states (LDOS) higher than that of the corresponding, bulk material. Additionally, we show that in addition to having an increased density of states, the absorber must have an appropriate incoupling mechanism to transfer light from free space into the optical modes of the device. We outline a portfolio of new solar cell designs that have potential to exceed the traditional light trapping limit and numerically validate our predictions for select cases.
\r\n\r\nWe emphasize the importance of thinking about light trapping in terms of maximizing the optical modes of the device and efficiently coupling light into them from free space. To further explore these two concepts, we optimize patterns of superlattices of air holes in thin slabs of Si and show that by adding a roughened incoupling layer the total absorbed current can be increased synergistically. We suggest that the addition of a random scattering surface to a periodic patterning can increase incoupling by lifting the constraint of selective mode occupation associated with periodic systems.
\r\n\r\nLastly, through experiment and simulation, we investigate a potential high efficiency solar cell architecture that can be improved with the nanophotonic light trapping concepts described in this thesis. Optically thin GaAs solar cells are prepared by the epitaxial liftoff process by removal from their growth substrate and addition of a metallic back reflector. A process of depositing large area nano patterns on the surface of the cells is developed using nano imprint lithography and implemented on the thin GaAs cells.
", "doi": "10.7907/Z92N506Z", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8718", "collection": "thesis", "collection_id": "8718", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10292014-120111728", "primary_object_url": { "basename": "Norte2014Thesis.pdf", "content": "final", "filesize": 76590438, "license": "other", "mime_type": "application/pdf", "url": "/8718/1/Norte2014Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Nanofabrication for On-Chip Optical Levitation, Atom-Trapping, and Superconducting Quantum Circuits \r ", "author": [ { "family_name": "Norte", "given_name": "Richard Alexander", "clpid": "Norte-Richard-Alexander" } ], "thesis_advisor": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Weinstein", "given_name": "Alan Jay", "orcid": "0000-0002-0928-6784", "clpid": "Weinstein-Alan-J-Physics" }, { "family_name": "Libbrecht", "given_name": "Kenneth George", "orcid": "0000-0002-8744-3298", "clpid": "Libbrecht-K-G" }, { "family_name": "Painter", "given_name": "Oskar J.", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_pma" } ], "abstract": "Researchers have spent decades refining and improving their methods for fabricating smaller, finer-tuned, higher-quality nanoscale optical elements with the goal of making more sensitive and accurate measurements of the world around them using optics. Quantum optics has been a well-established tool of choice in making these increasingly sensitive measurements which have repeatedly pushed the limits on the accuracy of measurement set forth by quantum mechanics. A recent development in quantum optics has been a creative integration of robust, high-quality, and well-established macroscopic experimental systems with highly-engineerable on-chip nanoscale oscillators fabricated in cleanrooms. However, merging large systems with nanoscale oscillators often require them to have extremely high aspect-ratios, which make them extremely delicate and difficult to fabricate with an \"experimentally reasonable\" repeatability, yield and high quality. In this work we give an overview of our research, which focused on microscopic oscillators which are coupled with macroscopic optical cavities towards the goal of cooling them to their motional ground state in room temperature environments. The quality factor of a mechanical resonator is an important figure of merit for various sensing applications and observing quantum behavior. We demonstrated a technique for pushing the quality factor of a micromechanical resonator beyond conventional material and fabrication limits by using an optical field to stiffen and trap a particular motional mode of a nanoscale oscillator. Optical forces increase the oscillation frequency by storing most of the mechanical energy in a nearly loss-less optical potential, thereby strongly diluting the effects of material dissipation. By placing a 130 nm thick SiO2 pendulum in an optical standing wave, we achieve an increase in the pendulum center-of-mass frequency from 6.2 to 145 kHz. The corresponding quality factor increases 50-fold from its intrinsic value to a final value of Qm = 5.8(1.1) x 105, representing more than an order of magnitude improvement over the conventional limits of SiO2 for a pendulum geometry. Our technique may enable new opportunities for mechanical sensing and facilitate observations of quantum behavior in this class of mechanical systems. We then give a detailed overview of the techniques used to produce high-aspect-ratio nanostructures with applications in a wide range of quantum optics experiments. The ability to fabricate such nanodevices with high precision opens the door to a vast array of experiments which integrate macroscopic optical setups with lithographically engineered nanodevices. Coupled with atom-trapping experiments in the Kimble Lab, we use these techniques to realize a new waveguide chip designed to address ultra-cold atoms along lithographically patterned nanobeams which have large atom-photon coupling and near 4\u03c0 Steradian optical access for cooling and trapping atoms. We describe a fully integrated and scalable design where cold atoms are spatially overlapped with the nanostring cavities in order to observe a resonant optical depth of d0 \u2248 0.15. The nanodevice illuminates new possibilities for integrating atoms into photonic circuits and engineering quantum states of atoms and light on a microscopic scale. We then describe our work with superconducting microwave resonators coupled to a phononic cavity towards the goal of building an integrated device for quantum-limited microwave-to-optical wavelength conversion. We give an overview of our characterizations of several types of substrates for fabricating a low-loss high-frequency electromechanical system. We describe our electromechanical system fabricated on a Si3N4 membrane which consists of a 12 GHz superconducting LC resonator coupled capacitively to the high frequency localized modes of a phononic nanobeam. Using our suspended membrane geometry we isolate our system from substrates with significant loss tangents, drastically reducing the parasitic capacitance of our superconducting circuit to \u2248 2.5$ fF. This opens up a number of possibilities in making a new class of low-loss high-frequency electromechanics with relatively large electromechanical coupling. We present our substrate studies, fabrication methods, and device characterization.", "doi": "10.7907/Z9WS8R61", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8736", "collection": "thesis", "collection_id": "8736", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12052014-101005469", "type": "thesis", "title": "Quantum Interference and Entanglement of Surface Plasmons", "author": [ { "family_name": "Fakonas", "given_name": "James Spencer", "clpid": "Fakonas-James-Spencer" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Fultz", "given_name": "Brent T.", "clpid": "Fultz-B-T" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Surface plasma waves arise from the collective oscillations of billions of electrons at the surface of a metal in unison. The simplest way to quantize these waves is by direct analogy to electromagnetic fields in free space, with the surface plasmon, the quantum of the surface plasma wave, playing the same role as the photon. It follows that surface plasmons should exhibit all of the same quantum phenomena that photons do, including quantum interference and entanglement.
\r\n\r\nUnlike photons, however, surface plasmons suffer strong losses that arise from the scattering of free electrons from other electrons, phonons, and surfaces. Under some circumstances, these interactions might also cause \u201cpure dephasing,\u201d which entails a loss of coherence without absorption. Quantum descriptions of plasmons usually do not account for these effects explicitly, and sometimes ignore them altogether. In light of this extra microscopic complexity, it is necessary for experiments to test quantum models of surface plasmons.
\r\n\r\nIn this thesis, I describe two such tests that my collaborators and I performed. The first was a plasmonic version of the Hong-Ou-Mandel experiment, in which we observed two-particle quantum interference between plasmons with a visibility of 93 \u00b1 1%. This measurement confirms that surface plasmons faithfully reproduce this effect with the same visibility and mutual coherence time, to within measurement error, as in the photonic case.
\r\n\r\nThe second experiment demonstrated path entanglement between surface plasmons with a visibility of 95 \u00b1 2%, confirming that a path-entangled state can indeed survive without measurable decoherence. This measurement suggests that elastic scattering mechanisms of the type that might cause pure dephasing must have been weak enough not to significantly perturb the state of the metal under the experimental conditions we investigated.
\r\n\r\nThese two experiments add quantum interference and path entanglement to a growing list of quantum phenomena that surface plasmons appear to exhibit just as clearly as photons, confirming the predictions of the simplest quantum models.
", "doi": "10.7907/Z9MG7MD3", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:7480", "collection": "thesis", "collection_id": "7480", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02152013-094838378", "type": "thesis", "title": "Advanced Silicon Solar Cell Device Physics and Design", "author": [ { "family_name": "Deceglie", "given_name": "Michael Gardner", "clpid": "Deceglie-Michael-Gardner" } ], "thesis_advisor": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "thesis_committee": [ { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "clpid": "Lewis-N-S" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A fundamental challenge in the development and deployment of solar photovoltaic technology is a reduction in cost enabling direct competition with fossil-fuel-based energy sources. A key driver in this cost reduction is optimized device efficiency, because increased energy output leverages all photovoltaic system costs, from raw materials and module manufacturing to installation and maintenance. To continue progress toward higher conversion efficiencies, solar cells are being fabricated with increasingly complex designs, including engineered nanostructures, heterojunctions, and novel contacting and passivation schemes. Such advanced designs require a comprehensive and unified understanding of the optical and electrical device physics at the microscopic scale. This thesis focuses on a microscopic understanding of solar cell optoelectronic performance and its impact on cell optimization. We consider this in three solar cell platforms: thin-film crystalline silicon, amorphous/crystalline silicon heterojunctions, and thin-film cells with nanophotonic light trapping. The work described in this thesis represents a powerful design paradigm, based on a detailed physical understanding of the mechanisms governing solar cell performance. Furthermore, we demonstrate the importance of understanding not just the individual mechanisms, but also their interactions. Such an approach to device optimization is critical for the efficiency and competitiveness of future generations of solar cells.", "doi": "10.7907/PV2J-1429", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" } ]