[ { "id": "authors:f4spp-ars50", "collection": "authors", "collection_id": "f4spp-ars50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140516-085207702", "type": "article", "title": "Design and characterization of whispering-gallery spiral waveguides", "author": [ { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Whispering gallery delay lines have demonstrated record propagation length on a silicon chip and can provide a way to transfer certain applications of optical fiber to wafer-based systems. Their design and fabrication requires careful control of waveguide curvature and etching conditions to minimize connection losses between elements of the delay line. Moreover, loss characterization based on optical backscatter requires normalization to account for the impact of curvature on backscatter rate. In this paper we provide details on design of Archimedean whispering-gallery spiral waveguides, their coupling into cascaded structures, as well as optical loss characterization by optical backscatter reflectometry.", "doi": "10.1364/OE.22.005196", "issn": "1094-4087", "publisher": "Optical Society of America", "publication": "Optics Express", "publication_date": "2014-03-10", "series_number": "5", "volume": "22", "issue": "5", "pages": "5196-5208" }, { "id": "authors:nwtxg-70584", "collection": "authors", "collection_id": "nwtxg-70584", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130925-141129867", "type": "article", "title": "Spiral resonators for on-chip laser frequency stabilization", "author": [ { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Suh", "given_name": "Myoung-Gyun", "orcid": "0000-0002-9527-0585", "clpid": "Suh-Myoung-Gyun" }, { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Li", "given_name": "Jiang", "clpid": "Li-Jiang" }, { "family_name": "Diddams", "given_name": "Scott A.", "orcid": "0000-0002-2144-0764", "clpid": "Diddams-S-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Frequency references are indispensable to radio, microwave and time keeping systems, with\nfar reaching applications in navigation, communication, remote sensing and basic science.\nOver the past decade, there has been an optical revolution in time keeping and microwave\ngeneration that promises to ultimately impact all of these areas. Indeed, the most precise\nclocks and lowest noise microwave signals are now based on a laser with short-term stability\nderived from a reference cavity. In spite of the tremendous progress, these systems remain\nessentially laboratory devices and there is interest in their miniaturization, even towards on-chip\nsystems. Here we describe a chip-based optical reference cavity that uses spatial\naveraging of thermorefractive noise to enhance resonator stability. Stabilized fibre lasers\nexhibit relative Allan deviation of 3.9x10^-13 at 400 micro\u00b5s averaging time and an effective\nlinewidth <100 Hz by achieving over 26 dB of phase-noise reduction.", "doi": "10.1038/ncomms3468", "pmcid": "PMC3778514", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2013-09", "series_number": "9", "volume": "4", "issue": "9", "pages": "Art. No 2468" }, { "id": "authors:7g0vg-pwr74", "collection": "authors", "collection_id": "7g0vg-pwr74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130226-152436926", "type": "article", "title": "Thermal stress in silica-on-silicon disk resonators", "author": [ { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "The thermal expansion mismatch of thermal grown silica on a silicon wafer is well known to induce compressive stress upon cooling from the growth temperature to room temperature. In this Letter, we investigate how this stress impacts silica disk structures by comparison of measurements with both a finite element and an analytical model. The disk structures studied are also whispering gallery optical resonators, and proper control of stress is critical to obtain high-Q resonances. Based on our analysis, thicker oxide layers and proper control of undercut enable ultra-high-Q optical performance and mechanical stability.", "doi": "10.1063/1.4789370", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "2013-01-21", "series_number": "3", "volume": "102", "issue": "3", "pages": "Art. No. 031113" }, { "id": "authors:9r90q-32x05", "collection": "authors", "collection_id": "9r90q-32x05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130110-084223375", "type": "article", "title": "Low-Pump-Power, Low-Phase-Noise, and Microwave to Millimeter-Wave Repetition Rate Operation in Microcombs", "author": [ { "family_name": "Li", "given_name": "Jiang", "clpid": "Li-Jiang" }, { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Microresonator-based frequency combs (microcombs or Kerr combs) can potentially miniaturize the numerous applications of conventional frequency combs. A priority is the realization of broadband (ideally octave spanning) spectra at detectable repetition rates for comb self-referencing. However, access to these rates involves pumping larger mode volumes and hence higher threshold powers. Moreover, threshold power sets both the scale for power per comb tooth and also the optical pump. Along these lines, it is shown that a class of resonators having surface-loss-limited Q factors can operate over a wide range of repetition rates with minimal variation in threshold power. A new, surface-loss-limited resonator illustrates the idea. Comb generation on mode spacings ranging from 2.6 to 220 GHz with overall low threshold power (as low as 1 mW) is demonstrated. A record number of comb lines for a microcomb (around 1900) is also observed with pump power of 200 mW. The ability to engineer a wide range of repetition rates with these devices is also used to investigate a recently observed mechanism in microcombs associated with dispersion of subcomb offset frequencies. We observe high-coherence phase locking in cases where these offset frequencies are small enough so as to be tuned into coincidence. In these cases, a record-low microcomb phase noise is reported at a level comparable to an open-loop, high-performance microwave oscillator.", "doi": "10.1103/PhysRevLett.109.233901", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2012-12-04", "series_number": "23", "volume": "109", "issue": "23", "pages": "Art. No. 233901" }, { "id": "authors:4xcph-hry80", "collection": "authors", "collection_id": "4xcph-hry80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121101-083137362", "type": "article", "title": "A general design algorithm for low optical loss adiabatic connections in waveguides", "author": [ { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Li", "given_name": "Jiang", "clpid": "Li-Jiang" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Single-mode waveguide designs frequently support higher order transverse modes, usually as a consequence of process limitations such as lithography. In these systems, it is important to minimize coupling to higher-order modes so that the system nonetheless behaves single mode. We propose a variational approach to design adiabatic waveguide connections with minimal intermodal coupling. An application of this algorithm in designing the \"S-bend\" of a whispering-gallery spiral waveguide is demonstrated with approximately 0.05dB insertion loss. Compared to other approaches, our algorithm requires less fabrication resolution and is able to minimize the transition loss over a broadband spectrum. The method can be applied to a wide range of turns and connections and has the advantage of handling connections with arbitrary boundary conditions.", "doi": "10.1364/OE.20.022819", "issn": "1094-4087", "publisher": "Optical Society of America", "publication": "Optics Express", "publication_date": "2012-09-24", "series_number": "20", "volume": "20", "issue": "20", "pages": "22819-22829" }, { "id": "authors:nvr0c-h9m82", "collection": "authors", "collection_id": "nvr0c-h9m82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121101-090149947", "type": "article", "title": "Characterization of a high coherence, Brillouin microcavity laser on silicon", "author": [ { "family_name": "Li", "given_name": "Jiang", "clpid": "Li-Jiang" }, { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Recently, a high efficiency, narrow-linewidth, chip-based stimulated Brillouin laser (SBL) was demonstrated using an ultra-high-Q, silica-on-silicon resonator. In this work, this novel laser is more fully characterized. The Schawlow Townes linewidth formula for Brillouin laser operation is derived and compared to linewidth data, and the fitting is used to measure the mechanical thermal quanta contribution to the Brillouin laser linewidth. A study of laser mode pulling by the Brillouin optical gain spectrum is also presented, and high-order, cascaded operation of the SBL is demonstrated. Potential application of these devices to microwave sources and phase-coherent communication is discussed.", "doi": "10.1364/OE.20.020170", "issn": "1094-4087", "publisher": "Optical Society of America", "publication": "Optics Express", "publication_date": "2012-08-27", "series_number": "18", "volume": "20", "issue": "18", "pages": "20170-20180" }, { "id": "authors:rvnzj-x9v98", "collection": "authors", "collection_id": "rvnzj-x9v98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120103-110617539", "type": "article", "title": "Chemically etched ultrahigh-Q wedge-resonator on a silicon chip", "author": [ { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Li", "given_name": "Jiang", "clpid": "Li-Jiang" }, { "family_name": "Yang", "given_name": "Ki Youl", "orcid": "0000-0002-0587-3201", "clpid": "Yang-Ki-Youl" }, { "family_name": "Jeon", "given_name": "Seokmin", "orcid": "0000-0002-1230-906X", "clpid": "Jeon-Seokmin" }, { "family_name": "Painter", "given_name": "Oskar", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Ultrahigh-Q optical resonators are being studied across a wide range of fields, including quantum information, nonlinear optics, cavity optomechanics and telecommunications. Here, we demonstrate a new resonator with a record Q-factor of 875 million for on-chip devices. The fabrication of our device avoids the requirement for a specialized processing step, which in microtoroid resonators8 has made it difficult to control their size and achieve millimetre- and centimetre-scale diameters. Attaining these sizes is important in applications such as microcombs and potentially also in rotation sensing. As an application of size control, stimulated Brillouin lasers incorporating our device are demonstrated. The resonators not only set a new benchmark for the Q-factor on a chip, but also provide, for the first time, full compatibility of this important device class with conventional semiconductor processing. This feature will greatly expand the range of possible 'system on a chip' functions enabled by ultrahigh-Q devices.", "doi": "10.1038/NPHOTON.2012.109", "issn": "1749-4885", "publisher": "Nature Publishing Group", "publication": "Nature Photonics", "publication_date": "2012-06", "series_number": "6", "volume": "6", "issue": "6", "pages": "369-373" }, { "id": "authors:zk8wf-h7r73", "collection": "authors", "collection_id": "zk8wf-h7r73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120625-102405306", "type": "article", "title": "Ultra-low-loss optical delay line on a silicon chip", "author": [ { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Li", "given_name": "Jiang", "clpid": "Li-Jiang" }, { "family_name": "Painter", "given_name": "Oskar", "orcid": "0000-0002-1581-9209", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Light propagation through an optical fibre causes a long, non-resonant (true) time delay used in numerous applications. In contrast to how it is deployed in optical communication systems, fibre is coiled in these applications to reduce footprint. This is a configuration better suited for a chip-based waveguide that would improve shock resistance, and afford the possibility of integration for system-on-a-chip functionality. However, integrated waveguide attenuation rates lag far behind the corresponding rates of optical fibre, featuring attenuation many orders larger. Here we demonstrate a monolithic waveguide as long as 27 m (39 m optical path length), and featuring broadband loss rate values of (0.08\u00b10.01) dB m^(\u22121) measured over 7 m by optical backscatter. Resonator measurements show a further reduction of loss to 0.037 dB m^(\u22121), close to that of optical fibres when first considered a viable technology. Scaling this waveguide to integrated spans exceeding 250 m and attenuation rates below 0.01 dB m^(\u22121) is discussed.", "doi": "10.1038/ncomms1876", "issn": "2041-1723", "publisher": "Nature Publishing Group", "publication": "Nature Communications", "publication_date": "2012-05-29", "volume": "3", "pages": "Art. No. 867" }, { "id": "authors:jejcn-y8k79", "collection": "authors", "collection_id": "jejcn-y8k79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110509-094316947", "type": "article", "title": "High sensitivity nanoparticle detection using optical microcavities", "author": [ { "family_name": "Lu", "given_name": "Tao", "clpid": "Lu-Tao" }, { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Herchak", "given_name": "Steven", "clpid": "Herchak-S" }, { "family_name": "Kim", "given_name": "Ji-Hun", "clpid": "Kim-Ji-Hun" }, { "family_name": "Fraser", "given_name": "Scott E.", "orcid": "0000-0002-5377-0223", "clpid": "Fraser-S-E" }, { "family_name": "Flagan", "given_name": "Richard C.", "orcid": "0000-0001-5690-770X", "clpid": "Flagan-R-C" }, { "family_name": "Vahala", "given_name": "Kerry", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "We demonstrate a highly sensitive nanoparticle and virus detection method by using a thermal-stabilized reference interferometer in conjunction with an ultrahigh-Q microcavity. Sensitivity is sufficient to resolve shifts caused by binding of individual nanobeads in solution down to a record radius of 12.5 nm, a size approaching that of single protein molecules. A histogram of wavelength shift versus nanoparticle radius shows that particle size can be inferred from shift maxima. Additionally, the signal-to-noise ratio for detection of Influenza A virus is enhanced to 38:1 from the previously reported 3:1. The method does not use feedback stabilization of the probe laser. It is also observed that the conjunction of particle-induced backscatter and optical-path-induced shifts can be used to enhance detection signal-to-noise.", "doi": "10.1073/pnas.1017962108", "pmcid": "PMC3076881", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2011-04-12", "series_number": "15", "volume": "108", "issue": "15", "pages": "5976-5979" }, { "id": "authors:vnamf-61777", "collection": "authors", "collection_id": "vnamf-61777", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110531-113003237", "type": "article", "title": "Compensation of thermal nonlinearity effect in optical resonators", "author": [ { "family_name": "Grudinin", "given_name": "Ivan", "clpid": "Grudinin-I-S" }, { "family_name": "Lee", "given_name": "Hansuek", "orcid": "0000-0002-0748-7662", "clpid": "Lee-Hansuek" }, { "family_name": "Chen", "given_name": "Tong", "clpid": "Chen-Tong" }, { "family_name": "Vahala", "given_name": "Kerry", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "abstract": "Thermal nonlinearity is known to cause bistability in Whispering Gallery Mode (WGM) resonators and to destabilize the red slope of the Lorentzian resonant curve. We demonstrate an optical technique that allows compensation of the thermal effect and forces the resonances to appear linear with both red and blue slopes stable.", "doi": "10.1364/OE.19.007365", "issn": "1094-4087", "publisher": "Optical Society of America", "publication": "Optics Express", "publication_date": "2011-04-11", "series_number": "8", "volume": "19", "issue": "8", "pages": "7365-7372" } ]