Silicon-on-insulator (SOI) provides an intriguing system for developing massively integrated optics. By leveraging the processes and systems developed for electronics fabrication, it is possible to make highly repeatable devices where complexity can be scaled up through the use of wafer-scale batch fabrication. Because the mode concentration in silicon waveguides is two orders of magnitude higher than in fibers, it is possible to construct very compact nonlinear optical devices within this system, enabling the miniaturization and integration of ultrafast nonlinear devices. We have developed a library of devices, including both dielectric and plasmonic waveguides, as well as resonators, splitters, and a variety of other basic optical components.
\r\n\r\nUsing these components to construct integrated devices of moderate complexity, we have demonstrated Pockels\u2019 Effect-based ring modulators, optical rectification-based detectors, four-wave mixing devices, and ultrafast intensity modulators, which operate at speeds in excess of 2 Terahertz. By integrating optical polymers through evanescent coupling to high-mode-confinement silicon waveguides, the effective nonlinearity of the waveguides can be greatly increased. The combination of high mode confinement, multiple integrated optical components, and high nonlinearity produces all-optical ultrafast devices operating at power levels compatible with modern continuous-wave telecommunication systems. Although far from commercial modulator standards in terms of extinction, these modulator devices are a first step toward large scale integrated ultrafast optical logic in silicon, and are two orders of magnitude faster than existing free-carrier-based silicon devices.
\r\n", "doi": "10.7907/8124-DA56", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:673", "collection": "thesis", "collection_id": "673", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02182006-133932", "primary_object_url": { "basename": "dissertation_final.pdf", "content": "final", "filesize": 1514037, "license": "other", "mime_type": "application/pdf", "url": "/673/1/dissertation_final.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Design and Analysis of High-Efficiency L-Band Power Amplifiers", "author": [ { "family_name": "Wang", "given_name": "Feiyu", "clpid": "Wang-Feiyu" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Moussessian", "given_name": "Alina", "clpid": "Moussessian-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Discrete solid-state high-power amplifiers are among the important circuit components in today\u2019s wireless communications and remote-sensing applications. As the device technologies continue to improve, there are new opportunities and new challenges presented to power amplifier designers. This thesis presents novel techniques in the design and the analysis of L-band high-efficiency power amplifiers, which may be used in many communications and radar applications.
\r\n\r\nIn this work, high-efficiency power amplifier topologies are discussed and implemented. The goal is to push the boundary of output power, operating frequency, efficiency and bandwidth. Also, the design of a key passive component, a balanced-to-unbalanced transformer (balun) is discussed in detail. Some new designs of the baluns are shown, and the results show advantages of these baluns over some of the traditional work at L-band.
\r\n\r\nThe stability analysis of power amplifiers is one of the most critical and the most challenging aspects of power amplifier design. This work shows an analysis technique, which accurately predicts the oscillations in power amplifiers. Using the technique, different stabilization techniques and circuits are designed and implemented.
", "doi": "10.7907/CJGR-TF04", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:5197", "collection": "thesis", "collection_id": "5197", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05242005-172142", "primary_object_url": { "basename": "thesis_ch1.pdf", "content": "final", "filesize": 273247, "license": "other", "mime_type": "application/pdf", "url": "/5197/1/thesis_ch1.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "A Solid-state Atomic Frequency Standard", "author": [ { "family_name": "White", "given_name": "Christopher John", "clpid": "White-Christopher-John" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Weitekamp", "given_name": "Daniel P.", "clpid": "Weitekamp-D-P" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Roukes", "given_name": "Michael Lee", "clpid": "Roukes-M-L" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The thesis describes a new class of frequency reference. The frequency source uses the same operating principle as a passive atomic frequency standard; however, the device is entirely solid-state, removing many cost and reliability issues associated with gas-phase atomic clocks. More specifically, the \"atomic resonance\" is derived from zero-field magnetic resonance transitions of the vanadium ion in a cubic crystal lattice. The characteristics of these resonances will be described in detail. The apparatus for measuring the \"atomic\" resonances uses a radio-frequency resonant cavity and frequency discriminator circuit. Using integrated circuits, the radio-frequency signal processing functions can be implemented at very low cost in a reliable manufacturing process. We discuss the system design and the measurement sensitivity. Advantages of the new frequency reference may include immunity to vibration and reduced aging compared to crystal oscillators.", "doi": "10.7907/ATKE-YX40", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2332", "collection": "thesis", "collection_id": "2332", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05312005-225644", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 2726540, "license": "other", "mime_type": "application/pdf", "url": "/2332/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Linearized and High Frequency Electrooptic Modulators", "author": [ { "family_name": "Cummings", "given_name": "Uri Vaughan", "clpid": "Cummings-Uri-Vaughan" } ], "thesis_advisor": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Schaffner", "given_name": "James H.", "clpid": "Schaffner-J-H" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "An analysis is performed of many standard and linearized electrooptic modulators known in the industry. The transfer functions of these modulators are evaluated under a consistent set of performance figures of merit, which are gain and spur-free dynamic range, using a canonical set of optical link parameters. The tolerance of the needed precision of the parameters of the linearization mechanisms of all of these modulators is compared over the entire interesting range of noise bandwidth.
\r\n\r\nA computer program was written to analyze the frequency dependence of any modulator transfer function under any set of functional inputs. The program is used to illustrate and compare the frequency dependence of the figures of merit of all of the modulators for which a d-c analysis was performed. Further analysis looks at the effect of greater noise-bandwidth and recovering the frequency-dependent degradation of gain and dynamic range through re-phasing techniques. The gain of directional couplers is analyzed in-depth.
\r\n\r\nTwo novel modulator schemes are produced. The first uses reflective wave techniques to retime the electrical and optical waves half way through the modulator. The second uses fabrication geometry and properties of the linearization technique to make a more robust modulator (applicable to three of the modulators analyzed).
\r\n\r\nA 94 GHz antenna-coupled directional coupler modulator was initially demonstrated using an old modulator chip from Finbar Sheehy. A peculiar bug with the chip was uncovered. And a new modulator experiment was constructed and many aspects of the experimental apparatus were optimized. Though the revised experiment ultimately did not yield modulation side bands, it did couple a 94 GHz microwave signal into the optical waveguide, and many interesting challenges of high frequency electrooptic modulator fabrication were evaluated and improved upon.
", "doi": "10.7907/GTD7-V873", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:5219", "collection": "thesis", "collection_id": "5219", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06012005-091623", "primary_object_url": { "basename": "Gunn_Thesis_20050523.pdf", "content": "final", "filesize": 9658401, "license": "other", "mime_type": "application/pdf", "url": "/5219/1/Gunn_Thesis_20050523.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Integration of Complex Optical Functionality in a Production CMOS Process", "author": [ { "family_name": "Gunn", "given_name": "Lawrence Cary, III", "clpid": "Gunn-Lawrence-Cary-III" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Yablonovitch", "given_name": "Eli", "clpid": "Yablonovitch-E" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical functionality has been developed within the confines of an existing CMOS process. As of this writing, 10Gigabit modulators, electrically tunable optical filters, waveguides, and grating coupler technology have been successfully implemented alongside the existing transistors in the Freescale Hip7SOI process. This technology will be used to manufacture high bandwidth optical interconnections directly on silicon chips, allowing a new type of network and computing infrastructure to be developed.
\r\n\r\nThis work is covered in two distinct phases. First, the exploratory work done to gain experience with high index contrast silicon waveguides primarily served to uncover challenges related with simulation of these devices, and with the practical limitations of efficiently coupling the resulting waveguide devices with the outside world.
\r\n\r\nThe second phase began as the grating coupler emerged to address the coupling challenge. It became feasible to conceive of a commercially viable technology based on silicon photonics. The coupler has been evolved to a high level, currently achieving coupling loss of less than 1dB. Once the light is on chip, filtering and modulation technology are implemented. The reverse-biased plasma dispersion modulator has a 3dB roll-off of 10GHz, and an insertion loss less than 5dB. Optical filters based on ring resonators, arrayed waveguide gratings, and interleavers have all been implemented, often with world record performance, and many of the devices have been made electronically tunable to compensate for manufacturing variations and environmental excursions.
\r\n\r\nFinally, circuitry has been designed and constructed on the same die with the optical functionality, fully demonstrating the ability to achieve monolithic integration of these devices.
", "doi": "10.7907/HKW9-4K53", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2296", "collection": "thesis", "collection_id": "2296", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05302003-160130", "primary_object_url": { "basename": "Dissertation_HuiWu.pdf", "content": "final", "filesize": 2612049, "license": "other", "mime_type": "application/pdf", "url": "/2296/1/Dissertation_HuiWu.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Signal Generation and Processing in High-Frequency / High-Speed Silicon-Based Integrated Circuits", "author": [ { "family_name": "Wu", "given_name": "Hui", "clpid": "Wu-Hui" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "High-frequency/high-speed integrated circuits become increasingly important because of the strong demand for higher data rate and lower power consumption, and they rely more on silicon-based technologies, which has the advantages of low cost, fast technological development and system-on-a-chip (SoC) capabilities. However, silicon technologies also present great challenges in high-frequency/high-speed integrated circuits. This work demonstrated that distributed circuit and injection locking are two enabling circuit techniques that can help overcome silicon limitations.
\r\n\r\nDistributed voltage-controlled oscillators (DVCO's) demonstrated the high-frequency capabilities of distributed circuits. The operation of distributed oscillators is analyzed and the general oscillation condition is derived, resulting in analytical expressions for the oscillation frequency and amplitude. Two tuning techniques are developed, namely, the inherent-varactor tuning and delay-balanced current-steering tuning. A complete analysis of the tuning techniques is also presented. CMOS and bipolar DVCO prototypes have been designed and fabricated in a commercial 0.35\u00b5m BiCMOS process. A 10-GHz CMOS DVCO achieves a tuning range of 12\\% and a phase noise of -103 dBc/Hz at 600 kHz frequency offset. A 12-GHz bipolar DVCO achieves a tuning range of 26% and a phase noise of -99 dBc/Hz at 600 kHz frequency offset. New DVCO architectures are also proposed to improve the performance.
\r\n\r\nThe distributed circuit technique is also used for equalization in high-speed fiber-optic systems, in which inter-symbol interference (ISI) caused by fibre dispersion imposes a major limitation. Compared to optical-domain methods and other electrical-domain methods, equalization with distributed transversal filters (DTF's) presents the most cost-effective and SoC-compatible solution. Prototype DTF's have been implemented in a commercial 0.18\u00b5m SiGe BiCMOS process for 10 Gpbs fiber-optic systems. A 7-tap DTF reduces the ISI of a 10 Gbps signal after 800m 50\u00b5m multi-mode fiber from 5 dB to 1.38 dB, and improves the BER from 10\u207b\u2075 to 10\u207b\u00b9\u00b2.
\r\n\r\nThe injection locking technique is applied in high-speed, low-power frequency dividers, namely, injection-locked frequency dividers (ILFD's). Based on the detailed analysis, shunt-peaking and oscillation-suppression techniques are developed to enhance the locking range. Prototypes are implemented in a commercial 0.35\u00b5m BiCMOS process using only CMOS transistors. A 19 GHz ILFD achieves a locking range of 1350 MHz with the power consumption of 1 mW. A 9 GHz ILFD achieves a locking range of 1490 MHz with the power consumption of 1.3 mW. Self-dividing oscillators are proposed to generate accurate low-phase-noise quadrature signals.
", "doi": "10.7907/51YY-3Y81", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:1867", "collection": "thesis", "collection_id": "1867", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05192003-161134", "primary_object_url": { "basename": "final_master.pdf", "content": "final", "filesize": 5040312, "license": "other", "mime_type": "application/pdf", "url": "/1867/1/final_master.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Waveguide Packaging of Quasi-Optical Grid Amplifiers", "author": [ { "family_name": "Cheung", "given_name": "Chun Tung", "clpid": "Cheung-Chun-Tung" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rosenberg", "given_name": "Jim", "clpid": "Rosenberg-J" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Quasi-optical amplifiers combining the output powers of hundreds of transistors have demonstrated the capability to deliver more than 10 Watts of power at millimeter wave frequencies. However, these amplifiers are large and expensive to manufacture. In this work, we attempt to find a compact, low-cost approach using metallic waveguide to package a grid amplifier. This thesis details the design and implementation of a grid amplifier packaged in waveguide. Frequency and time-domain simulation methods are used to calculate the field flatness and the small signal gain of the amplifier. Four different active grids packaged in waveguide will be reported. The first grid, operating at Ka-band, is fed with a waveguide and radiates its output into free space. The amplifier chip design was previously measured in free-space. This work demonstrates a small signal gain of 7 dB with output power of 5.5 W at 3-dB compression. The performance is similar to the same grid design measured in free-space. A second Ka-band grid amplifier packaged in waveguide for both input and output gives a small signal gain of 6 dB. The 3-dB compressed output power is 670 mW while the same amplifier measured in free-space gave 1.2 W output power. In order to further verify our active grid and packaging design methods, a V-band single-stage monolithic grid amplifier was designed and fabricated. A transmission grid amplifier and a reflection grid amplifier using this chip were fabricated. Both amplifiers have 2 dB small-signal gain at 58 GHz. In order to increase small-signal gain, a two-stage monolithic grid amplifier was designed and fabricated. A reflection approach was used to package this chip. Measured small-signal gain was 2.7 dB at 82 GHz.", "doi": "10.7907/KSGC-3G92", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:6372", "collection": "thesis", "collection_id": "6372", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05042011-091003477", "primary_object_url": { "basename": "Mumbru_j_2002.pdf", "content": "final", "filesize": 59845945, "license": "other", "mime_type": "application/pdf", "url": "/6372/1/Mumbru_j_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Optoelectronic Circuits Using Holographic Elements", "author": [ { "family_name": "Mumbr\u00fa", "given_name": "Jos\u00e9", "clpid": "Mumbr\u00fa-Jos\u00e9" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Bossaerts", "given_name": "Peter L.", "clpid": "Bossaerts-P-L" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Mok", "given_name": "Fai H.", "clpid": "Mok-Fai-H" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents the results of research in the use of holographic modules in optoelectronic systems, their applications, and the characterization of polymer materials on which to record volume holograms, for these modules. The first chapter makes the case that a direct interface between an optical memory and a chip integrating detectors and logic circuitry can better utilize the high parallelism inherent in holographic modules.\r\n\r\nThe second chapter introduces the idea of reconfigurable computing and Field Programmable Gate Arrays (FPGAs) as the framework in which to design a hybrid system, the\r\nOptically Programmable Gate Array (OPGA), that outperforms its electronic counterpart by reducing its reconfiguration time by three orders of magnitude. \r\n\r\nThe OPGA is the combination of three elements: an addressing device to selectively recall holographic data pages, an optical memory, and an optoelectronic chip. The third chapter investigates the issues related to each one of these elements and their integration in a compact module. Operation of the system is demonstrated by holographically programming the OPGA chip.\r\n\r\nIn the fourth chapter, experiments are performed to characterize the Aprilis ULSH500-7A photopolymer and study quantitatively its ability to store high-bandwidth\r\nholographic data pages. A method for hologram mastering and copying using Aprilis films is also demonstrated.\r\n\r\nChapter five investigates the recording and diffusional-amplification dynamics of the PQ-doped PMMA polymer. Different strategies to optimize the material by reducing\r\nthe duration of its post-exposure are examined, and the corresponding experimental results presented. The recording of strong gratings in samples of PQ-PMMA is tested to determine the suitability of this material for components in optical fiber networks.\r\n\r\nThe final chapter deals with applications and systems that can benefit from a direct interface with a holographic module. The use of optically programmable processors in the\r\nfield of neural prosthetics is explored. The design of a holographic 4-D microscope is presented and tested experimentally.\r\n", "doi": "10.7907/GM6Y-TE35", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:2944", "collection": "thesis", "collection_id": "2944", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-07202004-135306", "primary_object_url": { "basename": "Yao_t-j_2002.pdf", "content": "final", "filesize": 15797892, "license": "other", "mime_type": "application/pdf", "url": "/2944/1/Yao_t-j_2002.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Parylene for MEMS Applications", "author": [ { "family_name": "Yao", "given_name": "Tze-Jung", "clpid": "Yao-Tze-Jung" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Pine", "given_name": "Jerome", "clpid": "Pine-J" }, { "family_name": "Shumate", "given_name": "M.", "clpid": "Shumate-M" }, { "family_name": "Wu", "given_name": "Theodore Yao-tsu", "clpid": "Wu-T-Y-T" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The goal of this thesis is to utilize Parylene, a room-temperature chemical-vapor-deposited (CVD) polymer, for MicroElectroMechanical Systems (MEMS) applications. The identified unique properties of Parylene are used to fabricate various micromachining devices such as thermopneumatic microvalve, in-channel microflow restrictor, and electret microphones.\r\n\r\nFirst, the properties of Parylene as a MEMS material are reviewed. The electrical, thermal, surface, and mechanical properties are first compared with that of other materials and further studied specifically for MEMS applications. The high dielectric strength (determined as 250V/pm) of Parylene makes it suitable for use as an electrical insulation material. However, its high resistivity causes un-desired charging effects first described in polymer-based electrostatic devices. The undesired high pull-in voltage, \"bounce-back,\" and \"snap-down\" effects caused by dielectric charging are studied.\r\n\r\nSecond, to make Parylene as a surface-micromachined material, a process that overcomes the stiction problem has to be developed. Thus, a new technique that combines wet-acetone dissolution and dry BrF3 dry etching has developed to overcome the stiction problem, which prevents Parylene microstructures from freestanding. The devices of mm*mm size with high yield are demonstrated using this technology.\r\n\r\nA thermopneumatic microvalve with a corrugated silicone/Parylene composite membrane is designed, fabricated, and tested for gas flows of several slpm and inlet pressures of tens of psi. The lowest power consumption to turn off the gas flow is determined to be 73mW. A silicone-based microfluidic coupler, initially designed for microvalve packaging, is also demonstrated for its ability to connect the external macrofluidic world to microfluidic devices. The demonstrated \"quick-connect\" microfluidic coupler has low leakage, is reusable, and can maintain good seal up to 60 psi.\r\n\r\nAn in-channel microflow restrictor is also demonstrated with freestanding Parylene integration technology. The demonstrated restrictor can modulate flow at several tens of nl/min range with inlet pressures of several psi. The restrictor, although AC-actuated, can modulate the flow up to 50%.\r\n\r\nFinally, an electret microphone with thin-film Teflon AF is demonstrated. Parylene is shown to enhance the rigidity and yield of the microphone back plate. The demonstrated electret microphone has an open sensitivity of up to 45mV/Pa with a bandwidth of up to 10KHz.\r\n", "doi": "10.7907/caxb-sr18", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:5315", "collection": "thesis", "collection_id": "5315", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10212009-105023039", "primary_object_url": { "basename": "Sverdrup_l_2002.pdf", "content": "final", "filesize": 24649113, "license": "other", "mime_type": "application/pdf", "url": "/5315/1/Sverdrup_l_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Lower Hybrid Current Drive Experiments on the Encore Tokamak", "author": [ { "family_name": "Sverdrup", "given_name": "Lawrence Henry", "clpid": "Sverdrup-Lawrence-Henry" } ], "thesis_advisor": [ { "family_name": "Vreeland", "given_name": "Thad", "clpid": "Vreeland-T" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Corngold", "given_name": "Noel Robert", "clpid": "Corngold-N-R" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Vreeland", "given_name": "Thad", "clpid": "Vreeland-T" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The work of this thesis concerns a technological aspect of a tokamak fusion power reactor. A toroidal current in tokamaks is necessary for plasma equilibrium. Ohmic heated tokamaks are inherently pulsed devices since the toroidal plasma current is essentially a single turn secondary of a transformer. A pulsed power reactor is undesirable for a number of reasons including thermal fatigue to material structures and other mechanical cycling effects. Various means to drive a continuous current have been studied. One of the more successful schemes has been to inject unidirectional lower hybrid plasma waves into a tokamak. The plasma waves Landau damp on the high velocity tail of the electron distribution, delivering wave momentum to electrons and generating plasma current.
\r\n\r\nThe results of early experiments produced two plasma physics problems. First, the current drive effect disappeared above a certain plasma density that depended in some way on the particulars of the experiment. This effect became known as the 'density limit' problem. Secondly, the phase velocities of the launched lower hybrid plasma waves in most experiments turned out to be so high that essentially no electrons in the high velocity tail of the electron distribution were available to interact with the plasma waves. Despite this, large currents were indeed driven in most of the experiments. Somehow the 'spectral gap' between the launch phase velocity of the wave and the Landau damping phase velocity was being bridged.
\r\n\r\nExperiments at Caltech on the Encore tokamak failed to produce the large driven currents seen in other experiments. The reason for this and simultaneously the cause of the density limit seen in the other experiments was explained by a relatively simple and appealing theory.
\r\n\r\nSmall driven currents were observed. Initially puzzling was the result that currents could be driven in the same toroidal direction regardless of the directionality of the launched lower hybrid waves. The Encore tokamak had a handedness. The cause of this handedness turned out to be a radial, horizontal, magnetic error field associated with the toroidal magnetic field which led to a horizontal spiraling of the toroidal field lines.
", "doi": "10.7907/27RZ-SM06", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:2866", "collection": "thesis", "collection_id": "2866", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-07132001-112041", "primary_object_url": { "basename": "ashish_thesis.pdf", "content": "final", "filesize": 1170468, "license": "other", "mime_type": "application/pdf", "url": "/2866/1/ashish_thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "All-Optical Logic Circuits Based on the Polarization Properties of Non-Degenerate Four-Wave Mixing", "author": [ { "family_name": "Bhardwaj", "given_name": "Ashish Ishwar Singh", "clpid": "Bhardwaj-Ashish-Ishwar-Singh" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-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": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis investigates a new class of all-optical logic circuits that are based on the polarization properties of non-degenerate Four-Wave Mixing. Such circuits would be used in conjunction with a data modulation format where the information is coded on the states of polarization of the electric field. Schemes to perform multiple triple-product logic functions are discussed and it is shown that higher-level Boolean operations involving several bits can be implemented without resorting to the standard 2-input gates that are based on some form of switching. Instead, an entire hierarchy of more complex Boolean functions can be derived based on the selection rules of multi-photon scattering processes that can form a new class of primitive building blocks for digital circuits.
\r\n \r\nPossible applications of these circuits could involve some front-end signal processing to be performed all-optically in shared computer back-planes. As a simple illustration of this idea, a circuit performing error correction on a (3,1) Hamming Code is demonstrated. Error-free performance (Bit Error Rate of < 10\u207b\u2079) at 2.5 Gbit/s is achieved after single-error correction on the Hamming word with 50 percent errors. The bit-rate is only limited by the bandwidth of available resources. Since Four-Wave Mixing is an ultrafast nonlinearity, these circuits offer the potential of computing at several terabits per second. Furthermore, it is shown that several Boolean functions can be performed in parallel in the same set of devices using different multi-photon scattering processes. The main objective of this thesis is to motivate a new paradigm of thought in digital circuit design. Challenges pertaining to the feasibility of these ideas are discussed.
", "doi": "10.7907/CMAB-WF06", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:6152", "collection": "thesis", "collection_id": "6152", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10212010-100027618", "primary_object_url": { "basename": "Cai_m_2001.pdf", "content": "final", "filesize": 9944794, "license": "other", "mime_type": "application/pdf", "url": "/6152/1/Cai_m_2001.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Optical Fiber Taper Coupled Glass Microsphere Resonators", "author": [ { "family_name": "Cai", "given_name": "Ming", "clpid": "Cai-Ming" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "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": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis studies optical fiber taper coupled dielectric microsphere resonators and their applications. Fundamental properties including ideal coupling and critical coupling in an optical fiber taper to fused silica glass microsphere coupling system is investigated both theoretically and experimentally. A symmetrical dual-taper coupling configuration is proposed to obtain highly efficient power transfer from the taper coupler to the microsphere resonator. Applications as channel add/drop filters and microsphere lasers are also demonstrated.
\r\n\r\nThe physical essence of the fiber taper to silica microsphere is analyzed using a two-dimensional model. The relationship between the coupling strength and the cavity loss is unveiled. Adiabatic tapers and high-quality microspheres are fabricated and used to demonstrate actual coupling systems. Perfect agreement between the experimental results and the theoretical prediction is presented.
\r\n\r\nPower transfer from the taper to a microsphere resonator has been significantly improved by employing a dual-taper symmetrically coupling configuration. Up to -28 dB extinction at the central resonant wavelength has been measured.
\r\n\r\nWe then propose a device application of the taper-sphere-taper structure as a channel add/drop filter in the wavelength division multiplexing systems. For a filter with a bandwidth of 3.8 GHz and a dropping channel isolation of 26 dB, the bit-error-rate measurement shows no power penalty at 2.5 Gbit/s.
\r\n\r\nA 1.5 \u00b5m wavelength single-frequency fiber laser is also demonstrated using a single tapered fiber coupling to a highly doped erbium:ytterbium phosphate glass microsphere. The fiber taper serves the dual purpose of transporting optical pump power into the sphere and extracting the resulting laser emission. As low as 60 \u00b5W pump threshold and fiber-coupled output power as high as 3 \u00b5W with single mode operation are obtained. Imaging of photoluminescence from the sphere at visible wavelengths reveals the pump power is resonantly coupled into semiclassical orbits due to the strong absorption damping in the phosphate glass. A bi-sphere laser system consisting of two microspheres attached to a single fiber taper is also demonstrated.
\r\n\r\nFinally, a novel hybrid fiber taper, made from a combination of a 980 nm single mode fiber and a 1550 nm single mode fiber, is proposed and demonstrated as the microsphere laser coupler. Both the pump wave and laser emission are found to be more efficiently coupled to and from, respectively, the sphere modes. As high as 112 \u00b5W single-frequency laser output power is measured with a differential quantum efficiency of 12%.
", "doi": "10.7907/JB4C-VR78", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:1596", "collection": "thesis", "collection_id": "1596", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05032007-080831", "primary_object_url": { "basename": "Wong_jy_2000.pdf", "content": "final", "filesize": 22310563, "license": "other", "mime_type": "application/pdf", "url": "/1596/1/Wong_jy_2000.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Perpendicular patterned media for high density magnetic storage", "author": [ { "family_name": "Wong", "given_name": "Joyce Y.", "clpid": "Wong-J-Y" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Doll", "given_name": "Theodore", "clpid": "Doll-T" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Current longitudinal thin-film media in magnetic hard-disk drives are facing an oncoming limit caused by the superparamagnetic effect, in which the individual grains in the medium become so small that they are no longer stable against thermal fluctuation. This situation is undesirable as the stored information may be lost within an unexpectedly short time frame. There have been several proposed solutions in addressing the superparamagnetic limit, and one of them is perpendicular patterned media. In this approach, a periodic array of magnetic pillars is defined lithographically on a non-magnetic substrate. Binary data of \"1\" or \"0\" can be stored in each of these elements, which have two possible magnetization directions perpendicular to the plane of the medium.\n\nIn our perpendicular patterned media design, Ni columns of 150-230nm diameter with a 6:1 aspect ratio are embedded in an (AlGa)2O3/GaAs substrate. The fabrication procedure uses a combination of high resolution electron beam lithography, dry etching, and electroplating. The high aspect ratio in the column is achieved by taking advantage of the high etching rate and selectivity of AlGaAs/GaAs over (AlGa)203 in the Cl2 chemically assisted ion beam etching process. In addition to being a robust etching mask, the (AlGa)2O3 layer also plays an important role in the chemical mechanical polishing procedure to remove the overplated Ni mushrooms.\n\nOnce the Ni columns are fabricated, magnetic characterization is performed using magnetic force microscopy and scanning magnetoresistance microscopy. The former measurement confirms that the electroplated Ni columns are magnetic while the latter determines whether the individual columns are stable enough to retain the recorded information. We have successfully demonstrated recording in our 170nm diameter Ni column array arranged in a square format using a commercial read/write head. This is the first demonstration of single magnetic column per bit data storage in a prototype perpendicular patterned medium. Furthermore, we have recorded in higher density Ni column arrays in the form of tracks, corresponding to 1.3 and 2.6Gbits/in.2. Even though we are limited by the spatial resolution of the magnetoresistive read sensor, we have continued to pursue higher density structures up to an areal density of 350Gbits/in.2. Consideration of the issues in high resolution patterning and the magnetic stability of the individual columns have prompted researchers in the magnetic recording industry to anticipate the ultimate storage limit of perpendicular patterned media to be around 1Tbits/in.2", "doi": "10.7907/WEP6-MN90", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:225", "collection": "thesis", "collection_id": "225", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01182008-132046", "primary_object_url": { "basename": "Cheng_cc_1998.pdf", "content": "final", "filesize": 11218888, "license": "other", "mime_type": "application/pdf", "url": "/225/1/Cheng_cc_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Nanofabrication and Characterization of Photonic Crystals", "author": [ { "family_name": "Cheng", "given_name": "Chuan-cheng", "clpid": "Cheng-Chuan-cheng" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Both techniques and applications of nanofabrication have been explored in the field of periodic dielectric nanostructures. These periodic dielectric structures are expected to exhibit interesting properties in both fields of physics and engineering. These artificial nanostructures are named \"photonic crystals\" because photons demonstrate similar behavior in these structures as electrons in natural semiconductor crystals. In order to construct these crystals in the optical regime, suitable nanofabrication techniques have to be developed and demonstrated, including high resolution electron beam lithography and anisotropic chemically assisted ion beam etching. In this work, both 2D and 3D photonic crystals are fabricated and characterized in the near-infrared range.
\r\n\r\nIn the first part of this thesis, exploration of resolution limit of nanofabrication will be demonstrated and discussed. 15nm structures with 30nm period dot arrays and 20nm line width with 40mn period gratings are presented. Along with high resolution lithography, anisotropic pattern transfer is also developed. These powerful fabrication techniques enable us to miniaturize the dimension of both electronic and optical devices into the nanometer regime.
\r\n\r\nIn the second and third part of this thesis, detailed experiments and characterization of 2D and 3D photonic crystals are discussed. A brief introduction and a theoretical simulation are also presented. In the second part, computer generated form-birefringent nanostructures are first discussed and their performance demonstrated to agree well with design using rigorous coupled wave analysis (RCWA). In-plane 2D photonic crystals used as beam splitting micropolarizers are introduced and fabricated. High extinction ratios (>820:1) between transmitted TE and TM modes are measured. These in-plane photonic crystals are the first working devices using the idea of 2D photonic crystals. Three-dimensional artificial photonic crystals with a complete 3D bandgap represent a more attractive idea.
\r\n\r\nIn the third part of this thesis, we challenge the nanofabrication limits encountered when fabricating a 3D photonic crystal. The first three-dimensional photonic crystals with a forbidden photonic bandgap lying in the near infrared region of the electromagnetic spectrum, 1.1 \u03bcm < \u03bb < 1.5 \u03bc, just beyond the electronic band-edge of Gallium Arsenide (GaAs) are demonstrated in the world. These 3D photonic crystals were originally proposed by E. Yablonovitch and can now be fabricated using anisotropic angle etching at three directions through a hexagonal hole array mask. The field distribution using filtered finite-difference time-domain (FFDTD) calculation is briefly discussed. Development of the fabrication techniques and the optical transmission characterization are shown. Photonic crystals with up to six repeating layers are obtained and presented 90% attenuation of transmission measurement in the bandgap region. We also show the spectral shift in the transmission measurement corresponding with 2D lithographic control of microfabrication. Those artificial photonic crystals are expected to be useful in the study of inhibition of spontaneous emission and single-mode light-emitting diodes.
\r\n", "doi": "10.7907/sjy2-r565", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:3108", "collection": "thesis", "collection_id": "3108", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08132004-133148", "primary_object_url": { "basename": "Levene_m_1998.pdf", "content": "final", "filesize": 8023825, "license": "other", "mime_type": "application/pdf", "url": "/3108/1/Levene_m_1998.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Optics in neural computation", "author": [ { "family_name": "Levene", "given_name": "Michael", "clpid": "Levene-M" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Tanguay", "given_name": "Armand", "clpid": "Tanguay-A" }, { "family_name": "Fraser", "given_name": "Scott E.", "clpid": "Fraser-S-E" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In all attempts to emulate the considerable powers of the brain, one is struck by both its immense size, parallelism, and complexity. While the fields of neural networks, artificial intelligence, and neuromorphic engineering have all attempted oversimplifications on the considerable complexity, all three can benefit from the inherent scalability and parallelism of optics. This thesis looks at specific aspects of three modes in which optics, and particularly volume holography, can play a part in neural computation.\n\nFirst, holography serves as the basis of highly-parallel correlators, which are the foundation of optical neural networks. The huge input capability of optical neural networks make them most useful for image processing and image recognition and tracking. These tasks benefit from the shift-invariance of optical correlators. In this thesis, I analyze the capacity of correlators, and then present several techniques for controling the amount of shift invariance. Of particular interest is the Fresnel correlator, in which the hologram is displaced from the Fourier plane. In this case, the amount of shift invariance is limited not just by the thickness of the hologram, but by the distance of the hologram from the Fourier plane.\n\nSecond, volume holography can provide the huge storage capacity and high speed, parallel read-out necessary to support large artificial intelligence systems. However, previous methods for storing data in volume holograms have relied on awkward beamsteering or on as-yet non-existent cheap, wide-bandwidth, tunable laser sources. This thesis presents a new technique, shift multiplexing, which is capable of very high densities, but which has the advantage of a very simple implementation. In shift multiplexing, the reference wave consists of a focused spot a few millimeters in front of the hologram. Multiplexing is achieved by simply translating the hologram a few tens of microns or less. This thesis describes the theory for how shift multiplexing works based on an unconventional, but very intuitive, analysis of the optical far-field. A more detailed analysis based on a path-integral interpretation of the Born approximation is also derived. The capacity of shift multiplexing is compared with that of angle and wavelength multiplexing.\n\nThe last part of this thesis deals with the role of optics in neuromorphic engineering. Up until now, most neuromorphic engineering has involved one or a few VLSI circuits emulating early sensory systems. However, optical interconnects will be required in order to push towards more ambitious goals, such as the simulation of early visual cortex. I describe a preliminary approach to designing such a system, and show how shift multiplexing can be used to simultaneously store and implement the immense interconnections required by such a project.\n", "doi": "10.7907/XQVE-SA13", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:211", "collection": "thesis", "collection_id": "211", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01172008-081522", "primary_object_url": { "basename": "Shcheglov_kv_1997.pdf", "content": "final", "filesize": 13629071, "license": "other", "mime_type": "application/pdf", "url": "/211/1/Shcheglov_kv_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Synthesis, optical and electronic properties of group IV semiconductor nanocrystals", "author": [ { "family_name": "Shcheglov", "given_name": "Kirill Vadim", "clpid": "Shcheglov-Kirill-Vadim" } ], "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": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Quake", "given_name": "Stephen R.", "clpid": "Quake-S-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nEvery operating control system must deal with constraints. On the one hand, the range and rate of change of the input or manipulated variable is limited by the physical nature of the actuator (saturation limits). On the other hand, process state variables or outputs (pressures, temperatures, voltages) may not be allowed to exceed certain bounds arising from equipment limitation, safety considerations, or environmental regulations.\r\n\r\nA rich theory exists for designing controllers - both linear ([...],LQG, LTR, pole-placement) and nonlinear (nonlinear [...], control, feedback linearization, sliding mode control, gain scheduling). However, none of these popular and fashionable controller design techniques account for the presence of input or output constraints. Although occasionally these constraints may be neglected, in general, they lead to design and operating problems unless they are accounted for properly.\r\n\r\nIn traditional control practice, overrides or mode selection schemes are used to deal with output constraints: they switch between a \"bank\" of controllers, each of which is designed to achieve a specific objective. In both cases (saturation limit and mode selection), a control input nonlinearity is introduced into the operating system.\r\n\r\nDespite its significance, the study of the constrained control problem has received far less attention than the traditional unconstrained (linear and nonlinear) control theory. With few exceptions, most of the controller design techniques for constrained systems are by-and-large ad-hoc, with very little guarantees of stability, performance and robustness to plant model uncertainty.\r\n\r\nThe objective of this thesis is to take a broad approach towards the constrained control problem. One part of the thesis is devoted to the development of a systematic and unifying theory for studying the so-called Anti-Windup Bumpless Transfer (AWBT) problem. The other part aims towards the development of a general novel approach for the synthesis of a robust model predictive control (MPC) algorithm.\r\n\r\n\r\nNOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\r\n\r\nGroup IV semiconductor (Si, Ge and Sn) nanocrystals were synthesized in dielectric matrixes by ion implantation of the respective species into the matrix to form a supersaturated solid solution and subsequent precipitation by thermal annealing. The resulting structure was characterized by Transmission Electron Microscopy and Raman spectroscopy. It was found that nanocrystals of these materials can be effectively synthesized with diameters in the nanometer range. Ge nanocrystals in SiO[...] were extensively characterized, particle size distributions were counted from TEM results and were used to compare experimental photoluminescence spectra with theoretical predictions. Unusual nanostructures were formed in samples co-implanted with Ge and Sn and annealed at 600\u00b0C. Raman spectroscopy indicated a possibility of significant alloying of Ge and Sn in these nanostructures. Optical properties of Si nanocrystals in silicon dioxide were investigated by photoluminescence spectroscopy as well. It was found that while Ge nanocrystal system luminescence is mostly due to defects in the matrix produced by ion implantation, Si nanocrystal sample luminescence is due to the Si nanocrystals themselves. The luminescence is above the bulk Si bandgap and supports the quantum confined excitonic luminescence theory. Light emitting devices were fabricated using both systems. Electroluminescence was observed for both Si and Ge, albeit with rather low efficiency, in the 10[...] - 10[...] range. Electroluminescence from Si nanocrystal containing devices was spectrally similar to photoluminescence from that system, with a band about 800 nm, consistent with electronic excitation of radiative transitions in Si nanocrystals. Cubic nonlinearities were measured for both Ge and Si nanocrystals and found to be 10[...] - 10[...] esu range. Finally, an interesting interferometric arrangement which has a potential to be useful for investigating nanoscale structures was theoretically described.\r\n", "doi": "10.7907/59ar-ek67", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:5224", "collection": "thesis", "collection_id": "5224", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06072005-131657", "type": "thesis", "title": "Dynamics of Amplitude and Phase in Semiconductor Lasers and Effects of Propagation in Dispersive Optical Fibers", "author": [ { "family_name": "Marshall", "given_name": "William K.", "clpid": "Marshall-William-K" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Libbrecht", "given_name": "Kenneth George", "clpid": "Libbrecht-K-G" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The work described in this thesis occupies the region of overlap between the modulation, chirp, and noise properties of semiconductor lasers on one hand and dispersive propagation in optical fiber on the other. It is shown herein that simple relationships exist between the amplitude and phase variations of different kinds and that these relations lead to consequences of dispersive propagation which are different for the noise from semiconductor lasers than for the modulation. A range of topics related to the main theme of the interplay between laser chirp, amplitude-phase correlation, and dispersive propagation is considered. That there is much to be gained by understanding them together, as inter-related issues, is the overall conclusion.
\r\n\r\nFirst, changes in intensity variations which occur during dispersive propagation are described compactly in terms of a transfer function involving the relationship between amplitude and phase variations of the source. Then, the main dynamic characteristics of semiconductor lasers are described including the relationships between amplitude and phase variations produced by modulation and noise in semiconductor lasers. For an appropriate combination of laser and fiber parameters, it is demonstrated that the laser intensity noise can be reduced over a wide range of frequencies. It is also demonstrated that the change in relative intensity noise with propagation has a different dependence on laser and fiber parameters than does the change in modulation response. Next, the phenomenon of adiabatic compression of the gain and index of refraction in a semiconductor due to spectral hole burning is considered, clarifying some aspects of the commonly-used spectral hole burning model. Finally, the problem of the semiconductor laser and dispersive propagation of the output is re-examined within a quantum mechanical context and the input-output relations for the laser are explored.
", "doi": "10.7907/amwv-x166", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:115", "collection": "thesis", "collection_id": "115", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01102008-142830", "primary_object_url": { "basename": "Lee_rb_1997.pdf", "content": "final", "filesize": 6077138, "license": "other", "mime_type": "application/pdf", "url": "/115/1/Lee_rb_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "All-Optical Wavelength Conversion by Four-Wave Mixing in a Semiconductor Optical Amplifier", "author": [ { "family_name": "Lee", "given_name": "Robert Bumju", "clpid": "Lee-Robert-Bumju" } ], "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": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Quake", "given_name": "Stephen R.", "clpid": "Quake-S-R" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Wavelength division multiplexed optical communication systems will soon become an integral part of commercial optical networks. A crucial new function required in WDM networks is wavelength conversion, the spectral translation of information-laden optical carriers, which enhances wavelength routing options and greatly improves network reconfigurability. One of several techniques for implementing this function is four-wave mixing utilizing ultra-fast intraband nonlinearities in semicondutor optical amplifiers.
\r\n\r\nThe effects of input power, noise prefiltering and semiconductor optical amplifier length on the conversion efficiency and optical signal-to-noise ratio were examined. Systems experiments have been conducted in which several important performance characteristics of the wavelength converter were studied. A bit-error-rate performance of < 10-9 at 10 Gb/s was achieved for a record shift of 18 nm down in wavelength and 10 nm up in wavelength. Two cascaded conversions spanning a 40 km fiber link at 10 Gb/s are also demonstrated for conversions of up to 9 nm down and up in wavelength. The dynamic range of input signal power and its impact on the BER performance were studied at 2.5 Gb/s for both a single-channel conversion and a simultaneous 2-channel conversion. The crosstalk penalty induced by parasitic cross-gain modulation in 2-channel conversion is quantified. The spectral inversion which results from the conversion process is studied by time-resolved spectral analysis, and its application as a technique for dispersion compensation is demonstrated.
\r\n\r\nFinally, the application of selective organometallic vapor-phase epitaxy for the formation of highly-uniform and densely-packed arrays of GaAs quantum dots is demonstrated. GaAs dots of 15-20 nm in base diameter and 8-10 nm in height terminated by slow-growth crystallographic planes were grown within dielectric-mask openings and characterized by atomic force microscopy.
\r\n", "doi": "10.7907/4yye-5f58", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:5050", "collection": "thesis", "collection_id": "5050", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12182007-105428", "primary_object_url": { "basename": "Chiao_jc_1996.pdf", "content": "final", "filesize": 16166950, "license": "other", "mime_type": "application/pdf", "url": "/5050/1/Chiao_jc_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Quasi-optical components for millimeter and submillimeter waves", "author": [ { "family_name": "Chiao", "given_name": "Jung-Chih", "clpid": "Chiao-J" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Middlebrook", "given_name": "Robert David", "clpid": "Middlebrook-R-D" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nPower-combining schemes involving planar grids of solid-state devices or passive elements quasi-optically coupled in free space are an efficient means of combining power that makes them ideal for millimeter/submillimeter-wave applications by eliminating waveguide sidewall losses and machining difficulties. Three quasi-optical components including grid frequency multipliers, microswitch beam-steering grids and evanescent-wave couplers are presented.\n\nA terahertz grid frequency doubler using a 6x6 diode-grid periodically loaded with planar Schottky diodes has been developed. A peak output power of 330[...] was measured at 1.00 THz for 2.42-[...] 500-GHz input pulses with a peak power of 3.3 W.\n\nThe microswitch beam-steering grid has potential advantages over mechanical-scanning devices or active beam-steering reflectors based on diodegrids such as lower losses and simple control circuits at submillimeter wavelengths. Micromechanical electrostatically-controlled [...]-membrane switches have been fabricated on silicon wafers to provide binary reactance control. Simulations predict that a 4-bit controlled 10-layer microswitch beam-steering grid can have a phase-shift resolution of 22.5[...] over 360[...] with a maximum loss of 1.6 dB and a maximum phase error of 5[...] at 240 GHz.\n\nThe metal-mesh evanescent-wave couplers have been demonstrated to have wider bandwidths and larger modulations than Fabry-Perot couplers. The evanescent-wave coupling effect has been studied and used to increase the efficiency of an optically-controlled amplitude-modulator at 56.5 GHz.\n", "doi": "10.7907/qr6b-zk66", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:3146", "collection": "thesis", "collection_id": "3146", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08162007-095038", "primary_object_url": { "basename": "Weikle_rm_1992.pdf", "content": "final", "filesize": 6979106, "license": "other", "mime_type": "application/pdf", "url": "/3146/1/Weikle_rm_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Quasi-optical planar grids for microwave and millimeter-wave power combining", "author": [ { "family_name": "Weikle", "given_name": "Robert M.", "clpid": "Weikle-R-M" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" }, { "family_name": "Frerking", "given_name": "Margaret", "clpid": "Frerking-M" }, { "family_name": "Itoh", "given_name": "Tatsuo", "clpid": "Itoh-T" } ], "abstract": "Solid-state devices that produce radiation in the microwave and millimeter-wave region of the electromagnetic spectrum have relatively low power outputs compared to their electron-tube counterparts. In an attempt to obtain more power from solid-state sources, a number of power-combining schemes have been developed through the years. One of the most promising techniques involves superposing the outputs of many devices in free space. This quasi-optical approach has several advantages: the losses associated with waveguides and feed networks are eliminated, the power can be distributed over a large number of devices, and an external phase-locking signal is unnecessary. In this work, a method for quasi-optical power combining which is based on integrating devices into periodic grids is discussed. The approach is relatively simple to implement because the grid structures are planar. Thus they easily accommodate solid-state devices and allow for the possibility of wafer-scale integration. A method for analyzing the grids is presented and used to derive models for a variety of configurations. The validity of these models is investigated using a quasi-optical reflectometer. Designs and experimental results for MESFET oscillator grids operating in X-band and Ku-band are examined and discussed in detail.", "doi": "10.7907/K6WY-6V76", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:1577", "collection": "thesis", "collection_id": "1577", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05022006-155139", "type": "thesis", "title": "Photorefractive Volume Holography in Artificial Neural Networks", "author": [ { "family_name": "Brady", "given_name": "David Jones", "clpid": "Brady-David-Jones" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Bellan", "given_name": "Paul Murray", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Kimble", "given_name": "H. Jeff", "clpid": "Kimble-H-J" }, { "family_name": "Hopfield", "given_name": "John J.", "clpid": "Hopfield-J-J" }, { "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": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the use of volume holography to implement large-scale linear transformations on distributed optical fields. Such transformations are useful in the construction of hardware for artificial neural networks. The reconstruction of multiple grating holograms in layers of thin transparencies and in continuous volume media is considered and conditions under which such holograms may be used for linear transformations are derived. The control of the nature of the transformation implemented using fractal sampling grids is reviewed and the impact of such sampling grids on the energy efficiency of the overall system is considered. Information storage in volume holograms is shown to require multiple exposures and the impact of multiple exposures on linear hologram formations in saturable media and photorefractive materials is considered. It is shown for both types of media that the overall diffraction efficiency of a recorded hologram must decrease with the square of the rank of the transformation implemented. A theory for hologram formation in photorefractive materials with multiple trapping species is developed and compared with experimental results. The impact of multiple species and fixing mechanisms on linear hologram formation is evaluated. A method for refreshing the diffraction efficiency of photorefractive holograms in adaptive systems is described and demonstrated. The construction of thick holograms for linear transformations in waveguides is considered. A novel method for controlling such holograms is described and demonstrated. Learning in holographic neural networks is considered and two experimental holographic neural systems are described. The relative strengths of optical and electronic technologies for implementations of neural interconnections are considered.
", "doi": "10.7907/1YB6-SE42", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:700", "collection": "thesis", "collection_id": "700", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02212007-153159", "type": "thesis", "title": "GaAs/Al\u2093Ga\u2081\u208b\u2093As Quantum Well Lasers Grown on GaAs and Si by Molecular Beam Epitaxy", "author": [ { "family_name": "Chen", "given_name": "Howard ZeHua", "clpid": "Chen-Howard-ZeHua" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Molecular beam epitaxy (MBE) has been known as a \"black art\" since its invention in the early 1970's. The main goal of this thesis is to present practical techniques used daily MBE experts which have never been discussed in the literature. If this thesis can make a small step toward a better understanding and utilization of this technology, the author is more than satisfied.
\r\n\r\nThe following is a summary of experimental and theoretical work of GaAs-on-GaAs and GaAs-on-Si material growth by MBE. Except for the relatively new GaAs-on-Si research, background information is presented at a minimum level. Emphasis is made on both theoretical and experimental techniques rather than on general discussions which exist in the literature.
\r\n\r\nThe thesis begins with an introduction, in Chapter 1, to activities in molecular beam epitaxy and related crystal growth methods as well as their applications in the field of optical interconnects using low-threshold lasers and high-speed photodetectors.
\r\n\r\nIn Chapter 2, a Green's function formulation of interface matching problems is presented. A very simple equation can be derived, which can provide some support to a very controversial, yet highly successful and very popular quantum dipole model for Schottky barriers and heterojunctions by J. Tersoff. A simplified model can be obtained, which eliminates the uncertainties in Tersoff's scheme and predicts very well the band offsets for several important semiconductor heterosystems including GaAs/AlAs. The theory is found to be in excellent agreement with a photoelectric measurement on the band offsets of the GaAs/AlGaAs system.
\r\n\r\nChapter 3 deals with details of MBE growth of GaAs/AlGaAs quantum well laser material on GaAs substrates. Various growth techniques and substrate orientations are discussed. The dependence of threshold current density of a GaAs/AlGaAs GRINSCH laser on quantum well thickness is experimentally studied. The experimental results are in good agreement with a qualitative analysis. A theoretical discussion of the effect of quantum well thickness on the threshold current density is used to explain the experimental results. Furthermore, this study has achieved for the first time, threshold current densities below 100 A/cm\u00b2 in any semiconductor laser. The transparency current density obtained in this study, 60 A/cm\u00b2, is very close to the theoretical prediction of 63 A/cm\u00b2. It also establishes a record of lowest threshold current density for any semiconductor lasers.
\r\n\r\nChapter 4 presents some important issues in GaAs-on-Si research. Both the potentialities and limitations of GaAs-on-Si technology are discussed. The main advantage of GaAs-on-Si technology is the special features of Si substrates not available in GaAs substrates.
\r\n\r\nChapter 5 discusses the experimental aspects of GaAs-on-Si laser growth by MBE. The formation and prevention of antiphase domains (APDs) are discussed. Various methods to reduce defect density are presented. The first low threshold current density GaAs-on-Si laser growth by MBE, and the first room temperature continuous wave (CW) operation are described in detail. Important applications such as high-speed modulation of GaAs-on-Si stripe lasers and high-speed GaAs-on-Si p-i-n photodiodes are also presented.
\r\n\r\nAppendix I summarizes the operation and maintenance of a Riber 2300 MBE system from a practical point of view. Only several components in this MBE system are absolutely needed to grow high quality materials. It also discusses the routine material calibrations performed. Appendix II, III, IV, V, and VI deal with the details of material processing and device fabrication.
", "doi": "10.7907/thfh-4627", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:501", "collection": "thesis", "collection_id": "501", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02052007-093221", "type": "thesis", "title": "Properties of Buried Heterostructure Single Quantum Well (Al,Ga)As Lasers", "author": [ { "family_name": "Derry", "given_name": "Pamela Louise", "clpid": "Derry-Pamela-Louise" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Gould", "given_name": "Roy Walter", "clpid": "Gould-R-W" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Unlike conventional semiconductor lasers, single quantum well (SQW) lasers with high reflectivity end facet coatings have dramatically reduced threshold currents as a result of the smaller volume of the (active) quantum well region. A cw threshold current of 0.55 mA was obtained for a buried graded-index separate-confinement heterostructure SQW laser with facet reflectivities of ~80%, a cavity length of 120 \u00b5m, and an active region stripe width of 1 \u00b5m. This is believed to be the lowest threshold current so far reported for any semiconductor laser at room temperature.
\r\n\r\nThe submilliampere threshold currents of these lasers allow them to be modulated at high speed without any current prebias or feedback monitoring. The relaxation oscillation frequency for these lasers was also measured. Values of differential gain derived from these measurements demonstrated that the differential gain in the uncoated lasers is less than in the coated devices. This result was expected because of gain saturation.
\r\n\r\nAs predicted, SQW lasers have substantially narrower spectral linewidths than bulk double heterostructure lasers. This result is attributed to lower internal loss, linewidth enhancement factor, and spontaneous emission factor. A further major reduction (< 3x) in the linewidth of these SQW lasers was observed when the facet reflectivities were enhanced. This observation is explained theoretically on the basis of the very low losses in coated SQW lasers and the value of the spontaneous emission factor.
", "doi": "10.7907/WSZC-4R60", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:641", "collection": "thesis", "collection_id": "641", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02152007-083930", "type": "thesis", "title": "Modal Dispersal of Information and Wave Mixing in Photorefractive Crystals for Information Retrieval, Processing and Sensing", "author": [ { "family_name": "Tomita", "given_name": "Yasuo", "clpid": "Tomita-Yasuo" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes an experimental and theoretical study on modal dispersal of information and wave mixing in photorefractive crystals for vector phase conjugation and real-time information processing. Photorefractive crystals with short drift lengths (BaTiO\u2083 and Ba\u2081\u208b\u2093Sr\u2093Nb\u2082O\u2086) and long drift ones (Bi\u2081\u2082SiO\u2082\u2080 and semi-insulating GaAs) are particularly used in this thesis.
\r\n\r\nIn the first part, the photorefractive effect in electrooptic crystals is described in terms of Kukhtarev's band transport model. The explicit solution of the space-charge electric field for the case of one photorefractive species and one type of charge carrier is extended to the case of two photorefractive species and two types of charge carriers. The enhancement of the space-charge electric field is also described. In particular an approximate solution to Stepanov and Petrov's enhancement method of using AC external electric field is extended to a general case that describes the transient behavior for AC external electric field of arbitrary waveform. The anisotropic refractive index change due to the space-charge field formation is then described in terms of tensorial forms of the nonlinear susceptibility.
\r\n\r\nIn the second part, anisotropic beam coupling in photorefractive crystals is presented and a general set of coupled-wave equations that describes beam coupling in amplitude, phase, and polarization is derived by using the nonlinear and tensorial susceptibility. The polarization properties of the interacting waves are particularly stressed. Two limiting cases, i.e., one for scalar beam coupling and the other for cross-polarization beam coupling, are obtained from the general expression and solved. Experimental results of beam coupling in semi-insulating GaAs are presented, and the signs of dominant charge carriers and the density of photorefractive species are estimated from beam-coupling gain. The enhancement of beam-coupling gain and its temperature dependence are also discussed.
\r\n\r\nIn the third part, four-wave mixing for scalar and vector phase conjugation is described. Self-pumped phase-conjugate mirrors using photorefractive crystals are presented and one of the most interesting properties of these mirrors, i.e., the response to phase changes of inputs, is emphasized both theoretically and experimentally.
\r\n\r\nIn the fourth part, two-wave and four-wave mixing in photorefractive crystals are applied to moving object detection, mathematical operation on images, and one-way image transmission through phase-distorting media. In these applications, polarization properties of interacting waves are particularly utilized.
\r\n\r\nIn the fifth part, a novel method of vector phase conjugation by modal dispersal and scalar phase conjugation is discussed. The propagation characteristics of conjugate waves in strongly scattering media (e.g., mode-scrambling multimode fibers) are described theoretically, followed by the experimental demonstration of vector phase conjugation. In the theory the unitarity and time-reversal symmetry of the scattering matrix are incorporated into the analysis of the coherency matrix of the conjugate field. This theory which describes the physical process of the generation of vector phase conjugation can successfully explain the experimental results of its fidelity.
\r\n\r\nIn the last part, we describe experiments in which the new concept of modal dispersal of information and scalar phase conjugation is used for several novel applications that include nonreciprocal polarization-distortion correction, amplitude-distortion correction, and phase-conjugate multimode fiber-optic sensors. Experiments as well as proposals for these applications are presented.
", "doi": "10.7907/vjga-q464", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:646", "collection": "thesis", "collection_id": "646", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02162007-080706", "type": "thesis", "title": "Computer-Aided Measurement of Microwave Circuits", "author": [ { "family_name": "Williams", "given_name": "Wyman Lee", "clpid": "Williams-Wyman-Lee" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Middlebrook", "given_name": "Robert David", "clpid": "Middlebrook-R-D" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Instruments that measure the scattering parameters of microwave circuits generally have large systematic errors due to unavoidable parasitics in the instruments. These errors can be modeled analytically, however, and removed through a calibration procedure. A personal computer is well suited to the performance of the required calculations. Combining a personal computer with a microwave network analyzer results in a flexible and accurate automatic instrument. Two such automatic network analyzers are presented here. A new type of network analyzer, known as a sampled-line network analyzer is presented. It is an extension of the six-port network analyzer concept developed at the National Bureau of Standards. It is a particularly simple implementation and shows promise for the construction of relatively low-cost microwave network analyzers. The sampled-line network analyzer is analyzed theoretically and several experimental versions of it are presented. Another personal computer-controlled network analyzer is presented in which a Pascal program automates an HP 8410 network analyzer. The result is an instrument which can measure S-parameters from 0.5 to 18 GHz with a measurement error vector ranging in magnitude from 0.01 in the low frequency range to about 0.03 at 18 GHz.
", "doi": "10.7907/65XX-PQ66", "publication_date": "1989", "thesis_type": "phd", "thesis_year": "1989" }, { "id": "thesis:443", "collection": "thesis", "collection_id": "443", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02012007-140044", "type": "thesis", "title": "Optical Processing Using Photorefractive Crystals", "author": [ { "family_name": "Yu", "given_name": "Jeffrey Winston", "clpid": "Yu-Jeffrey-Winston" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Cohen", "given_name": "Donald S.", "clpid": "Cohen-D-S" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Breckinridge", "given_name": "James B.", "clpid": "Breckinridge-James-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The ability of photorefractive crystals to holographically record an optical image in real time allows one to use them in a variety of optical information processing systems. A number of such systems are presented in this thesis. To form the ground work used in analyzing the performance of photorefractive optical processors, a comparison between the Kukhtarev and Moharam models was done. The regimes where each model sufficiently predicted the response of the photorefractive crystal was determined. In addition, a new model based on a higher perturbation expansion of Kukhtarev's material equation is presented. This method allows one to numerically derive the profile of the space charge field recorded in the crystal and predict the regime where the Kukhtarev and Moharam models are most accurate.
\r\n\r\nThree optical processing systems are presented. The first, a photorefractive incoherent to coherent converter (PICOC), utilizes a photorefractive crystal as a spatial light modulator. Both the Kukhtarev and higher expansion models were used to analyze the performance of the converter. In the second example, the use of a photorefractive crystal as a time integrating detector is presented. By utilizing this crystal in an acousto-optic time integrating correlator, the output correlation is presented without the bias inherent in standard time integrating architectures. This allows one to utilize the full dynamic range of the output detector, thereby increasing the processing gain of the system. The third example utilizes a photorefractive crystal in a VanderLugt correlator. Standard VanderLugt correlators using planar holograms have been used successfully in pattern classification. In this thesis, we will derive the capacity of this system and demonstrate that by using a photorefractive crystal as the storage medium, the volume holographic properties of the crystal results in an increase in the capacity of the system. In addition, the angular selectivity of the crystal allows one to perform multi-category classification. The effect of using a volume hologram in a VanderLugt correlator is analyzed and experimental results presented.
", "doi": "10.7907/q49d-bb74", "publication_date": "1988", "thesis_type": "phd", "thesis_year": "1988" }, { "id": "thesis:827", "collection": "thesis", "collection_id": "827", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03012008-134009", "primary_object_url": { "basename": "Kasilingam_dp_1987.pdf", "content": "final", "filesize": 4261116, "license": "other", "mime_type": "application/pdf", "url": "/827/1/Kasilingam_dp_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Topics in Millimeter-Wave Imaging Arrays", "author": [ { "family_name": "Kasilingam", "given_name": "Dayalan P.", "clpid": "Kasilingam-Dayalan-P" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this thesis two different types of antenna arrays are investigated as possible configurations for two-dimensional diffraction limited imaging arrays. The first configuration is the \"fly's-eye\" array of microlenses. It is shown that this configuration may be utilized to achieve diffraction limited imaging with theoretical coupling efficiencies of around 50%. The other configuration is the two-dimensional horn array. It is shown that in this configuration, wide-angled horns etched into silicon achieve theoretical coupling efficiencies of 60%. A design for a two-dimensional imaging array, using horn elements of aperture size 1.5\u03bb0 was suggested. Also covered in this thesis are the radiation losses and the substrate-mode losses of coplanar transmission lines. It is shown that at millimeter-wave frequencies these losses are prohibitively high. Finally in the appendix a simulation of Schottky diode mixers is described as a possible design tool for analyzing millimeter-wave detector circuits.
", "doi": "10.7907/rt21-jt48", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:851", "collection": "thesis", "collection_id": "851", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03032008-105407", "primary_object_url": { "basename": "Lam_ww_1987.pdf", "content": "final", "filesize": 6134846, "license": "other", "mime_type": "application/pdf", "url": "/851/1/Lam_ww_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Millimeter-Wave Monolithic Schottky Diode-Grid Phase Shifter", "author": [ { "family_name": "Lam", "given_name": "Wayne W.", "clpid": "Lam-Wayne-W" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "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": "Luhmann", "given_name": "Neville C., Jr.", "clpid": "Luhmann-Neville-C-Jr" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Many applications at millimeter wavelengths require fast electronic phase shifters. In this study, the design of diode-grid phase shifters is presented, the fabrication of diode-grids on monolithic gallium-arsenide substrates is demonstrated, and the measurement of these grids is discussed. A new computer-aided design tool is developed to provide an interactive environment for design and to form a basis for comparing theory and experimental results. Diode-grids have been fabricated on 2 cm by 3 cm gallium-arsenide wafers with 2000 aluminum Schottky diodes. A novel small aperture reflectometer is computerized to use a wave-front division interference technique to measure the reflection coefficient of the grids. A 70\u00b0 phase shift with a 6.5-dB loss was measured at 93 GHz when the bias on the diode-grid was changed from -3V to +1V.
\r\n", "doi": "10.7907/CGD0-XA98", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:856", "collection": "thesis", "collection_id": "856", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03032008-143205", "primary_object_url": { "basename": "Lindsey_cp_1987.pdf", "content": "final", "filesize": 9992942, "license": "other", "mime_type": "application/pdf", "url": "/856/1/Lindsey_cp_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "High Power Phased Array and Tailored Gain Semiconductor Lasers", "author": [ { "family_name": "Lindsey", "given_name": "Christopher Paul", "clpid": "Lindsey-Christopher-Paul" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Cohen", "given_name": "Donald S.", "clpid": "Cohen-D-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Most phase locked semiconductor laser arrays suffer from undesirable twin lobed farfield patterns, making them unsuitable for many applications. In this thesis we make a detailed theoretical and experimental study of this problem, and solve it by tailoring the spatial gain profile across the array. We demonstrate a tailored gain chirped array which emits 450mW into a single beam 3\u00bd\u00b0 wide.
\r\n\r\nStripe geometry lasers for use in phased arrays are examined in Chapter 2, as are design considerations for evanescently coupled phased arrays. A powerful numerical method for analyzing a nearly arbitrary one-dimensional dielectric waveguide with gain and/or loss is described.
\r\n\r\nChapter 3 analyzes in detail the simplest array of two adjacent waveguides, both real index and gain guided and both weakly and strongly coupled. Chapter 4 discusses why a uniform array has a twin lobed farfield pattern, and introduces the concept of a nonuniform real index guided chirped array of lasers with widths which increase monotonically across the array. Real index guided chirped arrays can, in principle, be made to lase with a single lobed farfield pattern. Since such arrays are difficult to fabricate, and will be at least partially gain guided, we concentrate on gain guided structures. The combination of gain tailoring and a high interchannel gain in a proton implanted chirped array enables us to achieve our goal of fabricating a high power array with the single lobed farfield pattern described above.
\r\n\r\nSuch arrays are actually tailored gain broad area lasers. Chapter 5 demonstrates another method for gain tailoring, the \"halftone\" process, which can create nearly arbitrary two-dimensional spatial gain profiles in an optoelectronic device, thereby offering a new degree of freedom to the designer of semiconductor lasers. Single lobed nearly diffraction limited beams from tailored gain broad area lasers 50\u00b5m wide are obtained.
\r\n\r\nAsymmetric tailored gain waveguides have several unusual properties. The technique of Path Analysis for analyzing these complex waveguides is introduced. Fundamental Fourier Transform relationships relating device structure to farfield patterns yield additional insights. Finally, we close with a measurement of the antiguiding parameter and briefly examine some design criteria for practical tailored gain broad area lasers.
\r\n", "doi": "10.7907/9mh8-wv40", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:927", "collection": "thesis", "collection_id": "927", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03112008-080410", "primary_object_url": { "basename": "Zah_c_1986.pdf", "content": "final", "filesize": 7156226, "license": "other", "mime_type": "application/pdf", "url": "/927/1/Zah_c_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Millimeter-Wave Monolithic Schottky Diode Imaging Arrays", "author": [ { "family_name": "Zah", "given_name": "Chung-en", "clpid": "Zah-Chung-en" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Pine", "given_name": "Jerome", "clpid": "Pine-J" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Luhmann", "given_name": "Neville C., Jr.", "clpid": "Luhmann-Neville-C-Jr" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Inexpensive and compact imaging systems with high sensitivity are needed for millimeter waves. In this study, the calculated efficiencies of elementary integrated-circuit feed antennas show that the antennas with substrate lenses are potentially better feeds than those without substrate lenses. Planar Schottky diodes are integrated with bow-tie antennas to form a one dimensional array. The energy is focused onto the antenna through a silicon lens placed on the back of the gallium-arsenide substrate. Putting a polystyrene cap on the silicon lens has been demonstrated to be an effective way to reduce the reflection loss. A self-aligning process together with proton isolation has been developed to make the planar Schottky diodes with a 1.1-THz zero-bias cutoff frequency. The antenna coupling efficiency and imaging properties of the system are studied by video detection measurements at 94 GHz. As a heterodyne receiver, a double-sideband mixer conversion loss of 11.2 dB and noise temperature of 3770\u00b0K have been achieved at a local oscillator frequency of 91 GHz.
\r\n", "doi": "10.7907/YSN2-8F19", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1010", "collection": "thesis", "collection_id": "1010", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03192008-084301", "primary_object_url": { "basename": "Bruno_wm_1986.pdf", "content": "final", "filesize": 6311964, "license": "other", "mime_type": "application/pdf", "url": "/1010/1/Bruno_wm_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Powder Core Dielectric Waveguides", "author": [ { "family_name": "Bruno", "given_name": "William Michael", "clpid": "Bruno-William-Michael" } ], "thesis_advisor": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Pickett", "given_name": "Herbert M.", "clpid": "Pickett-H-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Flexible dielectric waveguides have been demonstrated at 10 GHz and 94 GHz by filling hollow, low dielectric constant polymer tubes with low-loss, high-dielectric constant powders. Flexible guides with losses as low as 0.12 dB/cm were demonstrated at 94 GHz. These guides also exhibited negligible bending loss for radii of curvature greater than 4 cm.
\r\n\r\nThe theory of 3-region cylindrical dielectric waveguide was used to design the powder-filled tube guides, and measured wavelengths for the HE11 mode are in agreement with theoretical values. Sets of dispersion curves were calculated numerically from the theory for waveguide parameters typical to our guides.
\r\n\r\nA powder-filled rectangular groove in the surface of a plastic substrate has also been demonstrated as a dielectric waveguide at 94 GHz. Guide wavelengths measured for these channel guides for various combinations of guide dimensions, powders, and substrate materials agree with values predicted by the approximate theory of Marcatili for the Ey11 mode. Measured transmission losses were as low as 0.09 dB/cm.
\r\n\r\nThe 94 GHz loss tangents of the powders were calculated by extending Marcatili's theory to relate channel guide attenuation to material losses. These calculated values of loss tangent increased with powder packing fraction, as predicted by theories of electromagnetic wave propagation in random heterogeneous media. Estimates of the 94 GHz loss tangents of the solid constituent materials were then obtained from these theories using the powder loss tangents.
\r\n\r\nPowder channel ring resonators had Q's as high as 2400 at 94 GHz in an 8 cm diameter ring. Directional coupling from adjacent straight channel guides was used to form a transmission filter. Marcatili's approximate theory of bending loss for channel guide appears to be inadequate for predicting the curvature losses of these resonators.
\r\n\r\nIn a 10 GHz experiment, the coupling between two parallel powder channel waveguides was measured as a function of their separation. The measured coupling was at variance with that predicted by Marcatili's approximate analysis for parallel channel waveguides.
", "doi": "10.7907/mxe4-ep43", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:3291", "collection": "thesis", "collection_id": "3291", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08312005-112325", "primary_object_url": { "basename": "Lang.1985.thesis_opt.pdf", "content": "final", "filesize": 6753876, "license": "other", "mime_type": "application/pdf", "url": "/3291/10/Lang.1985.thesis_opt.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Laser Doppler Velocity and Vorticity Measurements in Turbulent Shear Layers", "author": [ { "family_name": "Lang", "given_name": "Daniel Bernard", "clpid": "Lang-Daniel-Bernard" } ], "thesis_advisor": [ { "family_name": "Dimotakis", "given_name": "Paul E.", "clpid": "Dimotakis-P-E" } ], "thesis_committee": [ { "family_name": "Acosta", "given_name": "Allan J.", "clpid": "Acosta-A-J" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Roshko", "given_name": "Anatol", "clpid": "Roshko-A" }, { "family_name": "Dimotakis", "given_name": "Paul E.", "clpid": "Dimotakis-P-E" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A Laser Doppler Velocimeter (LDV) system was developed to measure the instantaneous spanwise vorticity, -wz, in a turbulent shear layer. It was necessary to design and fabricate the LDV optics and processing electronics, as no commercially available LDV systems met the specifications of measuring the velocity at four closely spaced points to the requisite accuracy. Measurements were also made of the instantaneous u, v, u', v', and -u'v'. The instantaneous vorticity was processed to obtain an estimate of its probability density function, from which the mean and rms values were estimated. It was also possible to separate the irrotational fraction of the flow (-wz \u2248 0) from the rotational (intermittent) fraction of the flow (-wz \u2260 0). The development of the intermittency profiles, based on vorticity, as a function of the downstream distance from the splitter plate was studied. A notable feature is that the vorticity is found to have values opposite the mean sense of rotation, i.e., -wz(t) < 0, a significant fraction of the time. Additionally, a detailed study was performed to evaluate the approximation of -\u2202v/\u2202x, in terms of various local temporal derivatives \u2202v/u(y)\u2202t. The optimum choice for u(y) can be found and is influenced by the relative local convection velocities of the small and large scale structures.
\r\n", "doi": "10.7907/YFR4-VE59", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:2669", "collection": "thesis", "collection_id": "2669", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06212004-160535", "primary_object_url": { "basename": "Prabhakar_a_1985.pdf", "content": "final", "filesize": 2906857, "license": "other", "mime_type": "application/pdf", "url": "/2669/1/Prabhakar_a_1985.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Investigations of Deep Level Defects in Semiconductor Material Systems", "author": [ { "family_name": "Prabhakar", "given_name": "Arati", "clpid": "Prabhakar-Arati" } ], "thesis_advisor": [ { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" } ], "thesis_committee": [ { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Janda", "given_name": "Kenneth C.", "clpid": "Janda-K-C" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this thesis, we present the results of two groups of investigations of deep level defects in semiconductor material systems.
\r\n\r\nChapter 1 consists of an overview of the thesis, background information on semiconductor impurities, and a description of deep level transient spectroscopy (DLTS).
\r\n\r\nChapter 2 contains discussions of the experiments performed on transition metal silicide-silicon Schottky barrier structures to probe for the existence of deep levels. We investigated platinum, palladium, and nickel silicides on n-type silicon which were annealed at temperatures from 300 to 800\u00b0C. The primary techniques used were DLTS, current-voltage (IV), and capacitance-voltage (C-V) measurements for electronic characterizations, and Rutherford backscattering spectrometry (RBS) to determine the silicide phase and film condition. For our samples, 700\u00b0C was the maximum temperature below which no significant degradation of the barrier or contamination of the underlying silicon were observed in platinum and palladium silicide structures. Nickel silicide structures could only withstand temperatures up to 500\u00b0C. Cobalt, chromium, and erbium silicides were also studied using DLTS. These measurements constitute the first series of studies of deep level contamination of the silicon underlying a transition metal suicide thin film.
\r\n\r\nChapter 3 details our DLTS studies of four different compositions of the alloy In1-xGaxAsyP1-y. Our samples, with bandgaps of 0.75, 0.83, 0.95,and 1.1 eV, covered the range of compositions that are lattice-matched to InP and are used for long-wavelength optoelectronic devices. No traps were observed above the detection limit of 5 x 1013 cm-3. The only exception was one sample, which had a trap that was attributed to a lattice defect in the substrate. These DLTS experiments were the first attempt to investigate deep level defects in In1-xGaxAsyP1-y.
\r\n", "doi": "10.7907/BNQT-B222", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:3155", "collection": "thesis", "collection_id": "3155", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08172005-102232", "primary_object_url": { "basename": "Tong_pp_1985.pdf", "content": "final", "filesize": 5850564, "license": "other", "mime_type": "application/pdf", "url": "/3155/1/Tong_pp_1985.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Millimeter-Wave Integrated-Circuit Antenna Arrays", "author": [ { "family_name": "Tong", "given_name": "Peter Ping Tak", "clpid": "Tong-Peter-Ping-Tak" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Knowles", "given_name": "James K.", "clpid": "Knowles-J-K" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents three different types of millimeter-wave integrated-circuit antenna array. They are a linearly polarized antenna array that can form polarization and intensity line images, a circularly polarized spiral antenna and a two-dimensional tracking antenna array. They are all integrated-circuit antennas with detectors on quartz substrates using quasi-optical systems to collect and focus the waves.
\r\n", "doi": "10.7907/ddxq-rj80", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:4494", "collection": "thesis", "collection_id": "4494", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11102005-144119", "primary_object_url": { "basename": "Greene_gj_1984.pdf", "content": "final", "filesize": 18562245, "license": "other", "mime_type": "application/pdf", "url": "/4494/1/Greene_gj_1984.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "ICRF Antenna Coupling and Wave Propagation in a Tokamak Plasma", "author": [ { "family_name": "Greene", "given_name": "Glenn Joel", "clpid": "Greene-Glenn-Joel" } ], "thesis_advisor": [ { "family_name": "Gould", "given_name": "Roy Walter", "clpid": "Gould-R-W" } ], "thesis_committee": [ { "family_name": "Gould", "given_name": "Roy Walter", "clpid": "Gould-R-W" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Corngold", "given_name": "Noel Robert", "clpid": "Corngold-N-R" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A variety of experiments are reported pertaining to the excitation, propagation, and damping of waves in the ion cyclotron range of frequencies (ICRF) in the Caltech Research Tokamak.
\r\n\r\nComplex impedance studies on five different RF antennas addressed the nature of the anomalous density-dependent background loading observed previously in several laboratories. A model was proposed which successfully explained many of the observed impedance characteristics solely in terms of particle collection and rectification through the plasma sheath surrounding the antenna electrode. Peaks were observed on the input resistance of the shielded antennas and were coincident with toroidal eigenmode production; their magnitude was explained by a simple coupling theory.
\r\n\r\nThe toroidal eigenmodes were studied in detail with magnetic field probes. The mode dispersion curves in density-frequency space were mapped out and the results compared with various theoretical models. A surprising result was that all of the antennas, both magnetic and electric in nature, coupled to the eigenmodes with comparable efficiency with respect to the antenna excitation current. Wave damping was investigated and found to be considerably higher than predicted by a variety of physical mechanisms. A numerical model of the wave equations permitting an arbitrary radial density profile was developed, and a possible mechanism for enhanced cyclotron damping due to density perturbations was proposed. Toroidal modes were identified using phase measurements between pairs of magnetic probes; they were found to have m = 1 poloidal character and low integral toroidal mode numbers, in accordance with theoretical predictions.
\r\n\r\nA new approach to the study of ICRF wave propagation was investigated: wave-packets were launched and their propagation was followed around the tokamak using magnetic probes. This technique avoided the dominant effect of the eigenmode resonances because it observed propagation on a time scale short compared to the formation time for the modes. The transit time of the packets around the machine yielded the toroidal group velocity, and the results of the experiments were compared with several theoretical models. The inclusion of a vacuum layer at the plasma edge was useful in explaining some of the observations.
\r\n\r\nFinally, a plasma-compatible Rogowski current probe was developed and used to observe, for the first time, RF particle current in a tokamak plasma. The diagnostic permitted investigation of the spatial form of the RF current driven in the edge plasma by the electric field antennas. The results dramatically showed that the current from these antennas flows largely along the toroidal field lines. This highly localized current distribution suggests a mechanism for the good coupling to the eigenmode fields observed with these antennas.
", "doi": "10.7907/ppan-gp26", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:295", "collection": "thesis", "collection_id": "295", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01232007-131641", "primary_object_url": { "basename": "Yu_kl_1984.pdf", "content": "final", "filesize": 4579274, "license": "other", "mime_type": "application/pdf", "url": "/295/1/Yu_kl_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Long Wavelength InGaAsP/InP Lasers and Optoelectronic Integration", "author": [ { "family_name": "Yu", "given_name": "Paul Kit-Lai", "clpid": "Yu-Paul-Kit-Lai" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Margalit", "given_name": "Shlomo", "clpid": "Margalit-Shlomo" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The light sources for optical communications in the 1.3-1.5 \u00b5m range are the quaternary InGaAsP/InP lasers which emit in this low loss region of optical fibers. The structure and properties of some lasers fabricated in this material system as well as their integration into optoelectronics are treated in this thesis.
\r\n\r\nLasers exhibiting low threshold, high power and stable far field are extremely desirable in communication systems. Selective epitaxial growth offers an elegant yet powerful technique of fabricating laser structures with these properties. Its application to, as well as properties of, the resulting laser structures are presented. In particular, a laser with high output power is demonstrated.
\r\n\r\nTo further extend the operating power of index guided laser diodes in a stable fundamental mode, gain stabilization is proposed as an effective means of discriminating against higher order transverse mode operation. The optimal design for gain stabilized fundamental mode operation is formulated theoretically and verified experimentally.
\r\n\r\nPrecipitous increase of threshold current with temperature has been observed in some InGaAsP/InP lasers. Electron leakage over the heterobarrier has been identified as the cause of this abnormality. The origin as well as the control of these leaked carriers is studied.
\r\n\r\nAdvances in optoelectronic integration consisting of diffraction coupled arrays and the demonstration of Laser-MISFET devices and the technique of microcleaved mirrors are described in detail.
\r\n\r\nThe microcleavage technique is applied to the fabrication of very short cavity lasers. The advantages of short cavities are presented.
\r\n", "doi": "10.7907/4dk7-wn36", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:84", "collection": "thesis", "collection_id": "84", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01092007-104136", "primary_object_url": { "basename": "Neikirk_dp_1984.pdf", "content": "final", "filesize": 14712401, "license": "other", "mime_type": "application/pdf", "url": "/84/1/Neikirk_dp_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Integrated Detector Arrays for High Resolution Far-Infrared Imaging", "author": [ { "family_name": "Neikirk", "given_name": "Dean Paul", "clpid": "Neikirk-Dean-Paul" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Pine", "given_name": "Jerome", "clpid": "Pine-J" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Imaging systems designed to operate in the millimeter and submillimeter portion of the spectrum (often referred to as the far-infrared) require the development of focal plane detector arrays to simplify their construction. In this study the general characteristics of an antenna array intended to provide diffraction limited imaging are discussed. Two line-imaging bow-tie antenna arrays utilizing the hyperhemispherical substrate lens optical system and operating at 1.22mm and 119\u00b5m, are demonstrated. Two new far-infrared detectors, the bismuth air-bridge microbolometer and the bismuth-antimony microthermocouple, have been used with these arrays. Thermal models and performance data for these detectors are given. Finally, the photolithographic processes used to fabricate the detectors and antennas are discussed.
\r\n", "doi": "10.7907/jxk1-9t91", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:240", "collection": "thesis", "collection_id": "240", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01192007-152414", "type": "thesis", "title": "Four-Wave Mixing and Phase Conjugation in Photorefractive Crystals", "author": [ { "family_name": "White", "given_name": "Jeffrey Owen", "orcid": "0000-0003-3109-193X", "clpid": "White-Jeffrey-Owen" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Kath", "given_name": "William L.", "clpid": "Kath-William-L" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is an experimental and theoretical investigation of nonlinear optics in photo-refractive crystals, and applications thereof. Coherent light is used to induce nonlinear, optical frequency polarizations proportional to the cube of the total optical field within these materials. Equivalently, dynamic holography performed wherein the incident light simultaneously writes, reads and erases index of refraction gratings.
\r\n\r\nThe first part of this thesis is a description of the physics of the photo-refractive effect in such crystals as Bi12SiO20, LiNbO3, KTaO3, and BaTiO3. Previous microscopic rate equation models are extended to include the dynamics of a second photo-refractive center with the aim of explaining several discrepancies with experimental data.
\r\n\r\nThe second part reviews the coupled wave theory of fixed gratings and dynamic gratings formed in photo-refractive media. Coupled nonlinear ordinary differential equations describe the interaction between two optical waves; which is caused by the grating that they create. The analysis is extended to the reflection geometry and the ring resonator geometry. The coupling constant is measured in the reflection geometry. Holographic gain is combined with mirror feedback to demonstrate a unidirectional ring oscillator, wherein a optically pumped photo-refractive crystal functions as a directional gain element.
\r\n\r\nThe third part extends the analysis to the holographic formulation of four-wave mixing, wherein four waves and up to four gratings exist in the crystal. The equations are solved in the single grating approximation. The object of much of the analysis is to calculate the reflectivity of a four-wave mixing photo-refractive phase conjugate mirror. The invention of a passive self-pumped phase conjugate mirror is described.
\r\n\r\nThe last part describes three applications of four-wave mixing. We demonstrate the compensation of intracavity laser distortions by replacing an ordinary mirror in a laser with a passive phase conjugate mirror. We propose and demonstrate a phase conjugate window for one-way transmission of an information bearing optical field through a thin phase distortion. Finally, the multiplicative properties of four-wave mixing are combined with the transforming properties of lenses to construct a coherent optical processor capable of convolving and correlating three input fields containing arbitrary spatial phase and amplitude information.
", "doi": "10.7907/f9ef-m894", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:1371", "collection": "thesis", "collection_id": "1371", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04132005-100141", "primary_object_url": { "basename": "Brooks_ed_1984.pdf", "content": "final", "filesize": 2739580, "license": "other", "mime_type": "application/pdf", "url": "/1371/1/Brooks_ed_1984.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Non-Perturbative Analysis of Some Simple Field Theories on a Momentum Space Lattice", "author": [ { "family_name": "Brooks", "given_name": "Eugene David, III", "clpid": "Brooks-Eugene-David-III" } ], "thesis_advisor": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Cowan", "given_name": "Eugene W.", "clpid": "Cowan-E-W" }, { "family_name": "George", "given_name": "Nicholas A.", "clpid": "George-N-A" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "In this work, we develop a new technique for the numerical study of quantum field theory. The procedure, borrowed from non-relativistic quantum mechanics, is that of finding the eigenvalues of a finite Hamiltonian matrix. The matrix is created by evaluating the matrix elements of the Hamiltonian operator on a finite basis of states. The eigenvalues and eigenvectors of the finite dimensional matrix become an accurate approximation to those of the physical system as the finite basis of states is extended to become more complete.
\r\n\r\nWe study a model of scalars coupled to fermions in 0+1 dimensions as a simple field theory to consider in the course of developing the technique. We find in the course of studying this model a change of basis which diagonalizes the Hamiltonian in the large coupling limit. The importance of this transformation is that it can be generalized to higher dimensional field theories involving a trilinear coupling between a Bose and a Fermi field.
\r\n\r\nHaving developed the numerical and analytical techniques, we consider a Fermi field coupled to a Bose field in 1+1 dimensions with the Yukawa coupling \u03bb\u03a8\u03a8\u03a8. We extend the large coupling limit basis of the 0+1 dimensional model to this case using a Bogoliubov transformation on the fermions. Although we do not use this basis in the numerical work due to its complexity, it provides a handle on the behavior of the system in the large coupling limit. In this model we consider the effects of renormalization and the generation of bound states.
", "doi": "10.7907/333S-XC47", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:4489", "collection": "thesis", "collection_id": "4489", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11102005-102554", "primary_object_url": { "basename": "Abushagur_ma_1984.pdf", "content": "final", "filesize": 4187857, "license": "other", "mime_type": "application/pdf", "url": "/4489/1/Abushagur_ma_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Scattering of Light from Large Cylinders", "author": [ { "family_name": "Abushagur", "given_name": "Mustafa A. G.", "clpid": "Abushagur-Mustafa-A-G" } ], "thesis_advisor": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "thesis_committee": [ { "family_name": "Cowan", "given_name": "Eugene W.", "clpid": "Cowan-E-W" }, { "family_name": "George", "given_name": "Nicholas A.", "clpid": "George-N-A" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Scattering of a plane electromagnetic wave from circular conducting and dielectric cylinders is analyzed. Both polarizations of the incident electric field, parallel and normal to the axis of the cylinder, are considered. The study of the rigorous solutions gives an insightful understanding of the scattered field and its dependence on the material of the cylinder, the polarizations of the incident field, and the three dimensionality of the object which usually are not considered in Fourier optics. It is shown that a combination of Fourier optics and ray theory can give good approximations for the scattered field from both conducting and dielectric cylinders. It is shown that the scattered pattern from a conducting cylinder consists of a main lobe and a number of side lobes. The spacing between the side lobes decreases as ka increases, where k is the wave number of the incident field and a the radius of the cylinder. It is found that for a certain conducting cylinder the side lobes terminate in a smaller scattering angle when the incident field is polarized parallel to the axis than when the incident field is polarized normal to the axis of the cylinder. The surface current density in the shadow region is found to be larger for the normal polarization case than for the parallel polarization case. The pattern of the scattered field from a dielectric cylinder has fringes all around the cylinder. The contrast of the fringes for the dielectric cylinder is much larger when the polarization of the incident field is parallel to the axis than that when the polarization is normal to the axis. The backscattered field of the dielectric cylinder has a peak which depends in its position on the refractive-index of the cylinder for the parallel polarization case. The fine structure of the scattering by a dielectric cylinder is studied. It is shown that the dielectric cylinder has resonant frequencies which depend on the radius and refractive-index of the cylinder. It is found that there are significant differences in the shape of the scattered pattern depending on whether the cylinder is at-resonance or at off-resonance. Experimental investigations are carried out to verify the theory derived in this study and it is found that both theory and experiments are in good agreement.
", "doi": "10.7907/akkw-r889", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:3373", "collection": "thesis", "collection_id": "3373", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09072006-080636", "type": "thesis", "title": "New Structures for AlGaAs Lasers and Avalanche Photodetectors", "author": [ { "family_name": "Blauvelt", "given_name": "Henry A.", "clpid": "Blauvelt-Henry-A" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McCaldin", "given_name": "James Oeland", "clpid": "McCaldin-J-O" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Goodstein", "given_name": "David L.", "clpid": "Goodstein-D-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the fabrication and the properties of five new semiconductor laser diode structures. All of these devices were grown from the GaAs-AlGaAs ternary system using the liquid phase epitaxial technique. In addition, a new low noise avalanche photodetector is proposed.
\r\n\r\nThe first example is a new technique for fabricating cleaved mirrors without cleaving through the substrate. This technique, called micro-cleavage, has potential applications for both opto-electronic integrated circuits and for the fabrication of short cavity length lasers. In this technique, cantilevers are formed by a sequence of etching steps. These cantilevers are subsequently cleaved using ultrasonic vibrations.
\r\n\r\nThree devices related to high power single mode lasers are described. The first of these is the large optical cavity buried heterostructure window laser. The output power of semiconductor lasers, particularly during pulsed operation is limited by catastrophic mirror damage which occurs at power densities above a pulse width dependent damage threshold. The damage occurs due to local heating up to the melting point of the active region in the vicinity of the cleaved mirror facets. However, catastrophic mirror damage can be avoided by isolating the active layer from the cleaved mirrors, as is done in these window lasers. The second device related to high power that is described is the Inverted Strip Buried Heterostructure laser. These lasers combine many of the best features of both the buried optical guide lasers and the strip buried heterostructure that have been previously developed elsewhere. The inverted strip buried heterostructure lasers have significantly better beam quality than buried optical guide lasers and can be operated in the fundamental spatial mode for larger emitting areas (and therefore greater output power). The third device related to high power lasers is a variation of a buried heterostructure laser in which the injected current is confined to a narrow section in the center of the active layer. The optical gain is therefore also confined to a narrow section in the center of the active layer. By doing so the fundamental mode is much better matched to the optical gain than the higher order spatial modes. The result is that fundamental mode operation is possible for buried heterostructure lasers with active layer widths up to 8 \u00b5m. When the current is injected uniformly into the active layer, fundamental mode operation is possible only for active layer widths less than 2 \u00b5m. In addition to the descriptions of these devices a theoretical chapter on high power single mode lasers is included.
\r\n\r\nThe final laser structure that is described is a single liquid phase epitaxial growth laser structure in which the current is restricted to flow between two narrow stripes located above and below the active layer. This structure, which is fabricated using a meltback-growth technique allows the current injection to be restricted to a very narrow section of the active layer, which results in several interesting properties which are described and explained using a simple model.
\r\n\r\nThe final subject of this thesis is a multilayer avalanche photodetector (APD) which has been proposed for low noise applications. The noise generated by an APD is dependent on the statistics of the carrier multiplication process, since positive feedback effects, which exist when both electrons and holes produce secondary pairs, can greatly amplify any current fluctuations. Significantly more noise is generated if the electron and hole ionization rates (\u03b1, \u03b2) are equal than if only one carrier produces secondary pairs. The multilayer structure described and analyzed in this chapter is expected to have impact ionization which is dominated by electrons and therefore would be of importance for low noise applications.
", "doi": "10.7907/DJMZ-S785", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3294", "collection": "thesis", "collection_id": "3294", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08312006-083650", "type": "thesis", "title": "I. Parametric Study of Optically Pumped Far-Infrared Waveguide Lasers. II. Theory and Experiment of Folded Fabry-Perot Quasi-Optical Ring Resonator Diplexer", "author": [ { "family_name": "Chiou", "given_name": "Arthur Er-Terg", "clpid": "Chiou-Arthur-Er-Terg" } ], "thesis_advisor": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "thesis_committee": [ { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Phillips", "given_name": "Thomas G.", "clpid": "Phillips-T-G" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis consists of two parts, each representing a different aspect of far-infrared (FIR) physics and technology.
\r\n\r\nPart I deals with the problems related to the physics and the design of one of the extremely useful coherent sources in the FIR region of the electromagnetic spectrum: the optically-pumped FIR waveguide laser. The effects of small waveguide diameter were studied here particularly because of their importance to the practical realization of a compact coherent FIR laser. Two known theoretical models were used to analyze the performance of CH3OH 118 \u00b5m laser and CH3F 496 \u00b5m laser; the results from these models were compared with the results of our experimental parametric study on CH3OH 118 \u00b5m laser. A simplified model of Lourtioz and Adde agrees reasonably well, in a semiquantitative sense, with our experimental results. The \u03bb2/a3 dependence of distributed waveguide loss for FIR radiation turns out to be the major factor that limits the waveguide size.
\r\n\r\nPart II deals with a problem related to the physics and design of a diplexer for application in the FIR heterodyne radiometry, where signals from the local oscillator and the received signal have to be directed into a detector for frequency mixing and for further signal processing. Since the signal of interest is typically very weak, the diplexer should serve the dual purpose of directing the two beams and filtering out the unwanted frequency components (noise) to enhance the signal to noise ratio, and do so with minimum loss.
\r\n\r\nThe optimum design parameters for a folded Fabry-Perot quasi-optical ring resonator diplexer were derived, and its performance was investigated both theoretically and experimentally. The results were compared with those of the similar diplexers of non-optimum geometry. The advantages and limitations of the optimum diplexer design are analyzed.
", "doi": "10.7907/eeh1-p029", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3920", "collection": "thesis", "collection_id": "3920", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10042006-130634", "type": "thesis", "title": "Gigawatt Picosecond Dye Lasers and Ultrafast Processes in Semiconductor Lasers", "author": [ { "family_name": "Koch", "given_name": "Thomas Lawson", "clpid": "Koch-Thomas-Lawson" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is a theoretical and experimental investigation of a gigawatt picosecond dye laser oscillator-amplifier system, and the application of that system to the study of ultrafast lasing and carrier dynamics in semiconductor lasers.
\r\n\r\nBeginning with a review of traveling wave rate equations, nonlinear pulse propagation in a generalized two-level amplifying/absorbing medium is discussed. This permits a qualitative treatment of synchronously mode-locked dye lasers. The formalism is then refined to provide a quantitative analysis of picosecond dye laser amplifier chains, including amplified spontaneous emission, saturable absorbers used for amplifier stage isolation, gain saturation with \"angular hole-burning\" and triplet losses, and linear and nonlinear pulse shaping effects.
\r\n\r\nExperimentally, the construction and operation of a three stage Nd:YAG laser pumped picosecond dye laser amplifier chain is described. Numerical modeling is used to compare the theoretical analysis with the experimental results. In addition, a brief discussion of picosecond time domain measurement techniques is presented, focussing on nonlinear optical methods. This includes a parametric sum frequency upconversion gating technique used extensively in this work to provide linear, picosecond resolution temporal measurements of optical pulses which are synchronized to the dye laser pulses.
\r\n\r\nThe output of the picosecond dye laser system is used to optically generate high carrier densities in semiconductor lasers, and the ensuing short pulse lasing dynamics are investigated and compared to the predictions of a simple rate equation analysis. Novel effects are observed in the spectrally resolved temporal measurements of the lasing output from picosecond optically pumped buried heterostructure semiconductor lasers. A model is developed which includes both broadband stimulated emission as well as many-valley and hot electron effects in the semiconductor, and the model is in close agreement with the observed behavior. The conclusion is drawn that the picosecond lasing dynamics of semiconductor lasers can be understood if the conventional rate equations are abandoned in favor of a more fundamental analysis which includes not just the dynamics of the optical energy exchange in the laser cavity, but the detailed picosecond dynamics of the semiconductor material as well.
\r\n", "doi": "10.7907/61ca-rp72", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:4566", "collection": "thesis", "collection_id": "4566", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11152004-162115", "type": "thesis", "title": "The Luminescent Solar Concentrator", "author": [ { "family_name": "Batchelder", "given_name": "John Samuel", "clpid": "Batchelder-John-Samuel" } ], "thesis_advisor": [ { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" } ], "thesis_committee": [ { "family_name": "Zewail", "given_name": "Ahmed H.", "clpid": "Zewail-A-H" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McCaldin", "given_name": "James Oeland", "clpid": "McCaldin-J-O" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The Luminescent Solar Concentrator (LSC) allows sunlight to be concentrated through the use of light pipe trapping of luminescence. Such concentrators do not require tracking, and they can reduce the cost of solar energy conversion by reducing the required area of photovoltaic cells. We have conducted the following experimental and theoretical investigations in order to optimize the LSC's performance.
\r\n\r\nThe spectral characteristics of 18 organic laser dyes are studied for their applicability as luminescing centers. The spectral homogeneity and self-absorption characteristics of representative dyes are examined in detail. The relative spectral homogeneity of such dyes is shown to depend upon the surrounding material using narrow band laser excitation. We develop three independent techniques for measuring self-absorption rates; these are time-resolved emission, steady state polarization anisotropy, and spectral convolution. Prototype devices are tested for performance, and the componant dyes are tested for stability to solar exposure.
\r\n\r\nA model is developed which predicts the efficiency and gain of and LSC from the spectroscopic characteristics of its components. A critical optical density (CODE) is assigned to the dyes surveyed which predicts the self-absorption limited performance for a particular dye. The maximum efficiency of an LSC is found using a simple model and the experimentally measured Stokes shift required to minimize self-absorption.
\r\n\r\nWe find that the performance of LSCs which achieve high light concentration is primarily limited by self-absorption and by photodegradation. The maximum efficiency possible is about 9% in such systems, and present devices can achieve about 3%. A typical lifetime for an LSC using organic laser dyes due to photodegradation is on the order of a month.
", "doi": "10.7907/W5W7-9660", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:2494", "collection": "thesis", "collection_id": "2494", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06072006-091651", "type": "thesis", "title": "Optoacoustic Detection Employing Stark Voltage Modulation and Stark Polarization Modulation", "author": [ { "family_name": "Kavaya", "given_name": "Michael Joseph", "clpid": "Kavaya-Michael-Joseph" } ], "thesis_advisor": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Menzies", "given_name": "Robert Thomas", "clpid": "Menzies-Robert-Thomas" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The conventional chopped laser radiation technique of optoacoustic detection suffers from a sensitivity-limiting synchronous background signal. This thesis reports on theoretical and experimental studies of two novel optoacoustic modulation techniques designed to reduce the background signal and thereby improve the sensitivity. A specialized optoacoustic detector is described, which is capable of being operated in the conventional chopped-laser modulation mode as well as in the new Stark voltage modulation and Stark polarization modulation modes; experimental results are given using all three modes of operation. Stark voltage modulation produces more than two orders of magnitude improvement in sensitivity over conventional modulation under identical conditions. Even greater sensitivities are shown to be attainable. A basic theory of conventional optoacoustic detection is developed and then applied to the new optoacoustic modulation techniques. An introduction to and history of optoacoustic detection are also presented.
", "doi": "10.7907/JB2P-3726", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3363", "collection": "thesis", "collection_id": "3363", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-152644", "type": "thesis", "title": "Dielectric Waveguides for Millimeter Waves", "author": [ { "family_name": "Schweig", "given_name": "Edgard", "clpid": "Schweig-Edgard" } ], "thesis_advisor": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "thesis_committee": [ { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Keller", "given_name": "Herbert Bishop", "clpid": "Keller-H-B" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this thesis, we analyze high-permittivity dielectric waveguides for use as guiding structures of millimeter waves. Two basic geometries are considered: the circular and rectangular guides.
\r\n\r\nIn Part I, we describe the theory of round fibers surrounded by an infinite cladding. Millimeter wavelengths are comparable to the physical dimensions of the guide. Therefore, a large difference in permittivity between the core and the cladding is required in order to provide for a tight confinement of the fields. We present the results of computations of the propagation characteristics and losses of fibers of very high permittivity. We note that the distribution of the electromagnetic power between the core and the cladding can be deduced from the dispersion curves. Finally, we consider the feasibility of a dielectric fiber made of thallium bromide-iodide (KRS-5) for the long distance transmission of W-band signals (94 GHz). Using our measurements of the dielectric parameters of KRS-5, we find that the losses are several orders of magnitude higher than the losses of conventional metallic waveguides.
\r\n\r\nIn Part II, we analyze rectangular dielectric guides made of high-permittivity materials such as GaAs that would permit the fabrication of active devices directly into the transmission line. We present a new numerical technique base on finite-differences for computing the modes of dielectric guiding structures. This method is simple and efficient in computer storage and computational time. We use it to compute the modes of a rectangular dielectric waveguide and compare the numerical results to those obtained from Marcatili's closed-form solution. We find that this latter one is a good approximation for the dominant mode of a rectangular guide even when the permittivity of the guide is large compared to the outer medium. For higher order modes, Marcatili's solution predicts incorrect propagation curves. We have also observed the presence in our numerical solution of \"spurious modes\" that are thought to be due to the mathematical indefinitiveness of the problem.
\r\n\r\nIn Part III, we present a waveguide technique for the measurement of complex dielectric constants at millimiter wave frequencies: the shorted-waveguide method. Waveguide methods have been extensively used at lower frequencies but this is the first application at 94 GHZ. We use a novel sample preparation technique that allows for an accurate and gap-free positionment of a ductile dielectric material inside a metallic waveguide. We note that the correct choice of sample lengths is critical to the accuracy of the measurement of the loss tangent. Finally, we summarize the results of our measurement of the dielectric constant and loss tangent of thallium bromide-iodide (KRS-5) and thallium bromide-chloride (KRS-6).
", "doi": "10.7907/05DR-KV58", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3519", "collection": "thesis", "collection_id": "3519", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09132006-133617", "type": "thesis", "title": "Long Wavelength GaInAsP/InP Semiconductor Lasers for Optical Communications", "author": [ { "family_name": "Chen", "given_name": "Pei-Chuang", "clpid": "Chen-Pei-Chuang" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical fiber communication systems have shifted toward the long wavelength range of 1.2-1.6 \u00b5m due to lower losses and dispersion available with high quality fibers. The quaternary GaInAsP/InP material system has evolved as the most promising system for light sources in this range.
\r\n\r\nIndium phosphide electronic devices are expected to possess high frequency switching capabilities, but present device technology is still rather primitive. In anticipation of future developments, which will render opto-electronic integration in this system advantageous, two laser structures on semi-insulating InP substrates were demonstrated. The substrate permits electrical isolation between components and thus is ideal in planar integration of the lasers with electronic devices.
\r\n\r\nLow threshold lasers can only be achieved when the active region is properly defined in two dimensions to provide good optical and carrier confinement. Present techniques usually require difficult and intricate growth step of two-step liquid phase epitaxy. Embedded epitaxy, by growth through a mask, offers a simple yet elegant means of two dimensional definition of the active region with only a single growth step. Low threshold lasers were fabricated with this technique and demonstrated its potential applications.
\r\n\r\nAll GaInAsP/InP lasers show accelerated increase of threshold current with temperature of a different nature than similar GaA1As lasers. To understand the origin of this phenomenon, calculations were made of the Auger process in these lasers, and have demonstrated that they play a very important role in the temperature behavior of GaInAsP/InP lasers.
\r\n", "doi": "10.7907/51sv-sm58", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:8081", "collection": "thesis", "collection_id": "8081", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02182014-143316560", "primary_object_url": { "basename": "Nilsen_jm_1982.pdf", "content": "final", "filesize": 31204492, "license": "other", "mime_type": "application/pdf", "url": "/8081/1/Nilsen_jm_1982.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Phase Conjugation via Four-Wave Mixing in a Resonant Medium", "author": [ { "family_name": "Nilsen", "given_name": "Joseph Michael", "clpid": "Nilsen-Joseph-Michael" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" }, { "family_name": "Frautschi", "given_name": "Steven C.", "clpid": "Frautschi-S-C" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This thesis describes the theoretical solution and experimental verification of phase conjugation via nondegenerate four-wave mixing in resonant media. The theoretical work models the resonant medium as a two-level atomic system with the lower state of the system being the ground state of the atom. Working initially with an ensemble of stationary atoms, the density matrix equations are solved by third-order perturbation theory in the presence of the four applied electro-magnetic fields which are assumed to be nearly resonant with the atomic transition. Two of the applied fields are assumed to be non-depleted counterpropagating pump waves while the third wave is an incident signal wave. The fourth wave is the phase conjugate wave which is generated by the interaction of the three previous waves with the nonlinear medium. The solution of the density matrix equations gives the local polarization of the atom. The polarization is used in Maxwell's equations as a source term to solve for the propagation and generation of the signal wave and phase conjugate wave through the nonlinear medium. Studying the dependence of the phase conjugate signal on the various parameters such as frequency, we show how an ultrahigh-Q isotropically sensitive optical filter can be constructed using the phase conjugation process.
\r\n\r\nIn many cases the pump waves may saturate the resonant medium so we also present another solution to the density matrix equations which is correct to all orders in the amplitude of the pump waves since the third-order solution is correct only to first-order in each of the field amplitudes. In the saturated regime, we predict several new phenomena associated with degenerate four-wave mixing and also describe the ac Stark effect and how it modifies the frequency response of the filtering process. We also show how a narrow bandwidth optical filter with an efficiency greater than unity can be constructed.
\r\n\r\nIn many atomic systems the atoms are moving at significant velocities such that the Doppler linewidth of the system is larger than the homogeneous linewidth. The latter linewidth dominates the response of the ensemble of stationary atoms. To better understand this case the density matrix equations are solved to third-order by perturbation theory for an atom of velocity v. The solution for the polarization is then integrated over the velocity distribution of the macroscopic system which is assumed to be a gaussian distribution of velocities since that is an excellent model of many real systems. Using the Doppler broadened system, we explain how a tunable optical filter can be constructed whose bandwidth is limited by the homogeneous linewidth of the atom while the tuning range of the filter extends over the entire Doppler profile.
\r\n\r\nSince it is a resonant system, sodium vapor is used as the nonlinear medium in our experiments. The relevant properties of sodium are discussed in great detail. In particular, the wavefunctions of the 3S and 3P states are analyzed and a discussion of how the 3S-3P transition models a two-level system is given.
\r\n\r\nUsing sodium as the nonlinear medium we demonstrate an ultrahigh-Q optical filter using phase conjugation via nondegenerate four-wave mixing as the filtering process. The filter has a FWHM bandwidth of 41 MHz and a maximum efficiency of 4 x 10-3. However, our theoretical work and other experimental work with sodium suggest that an efficient filter with both gain and a narrower bandwidth should be quite feasible.
\r\n\r\n\r\n\r\n", "doi": "10.7907/RV9B-GV44", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:3523", "collection": "thesis", "collection_id": "3523", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09132006-153307", "type": "thesis", "title": "Measurements of Magnetic Field Fluctuations in the Caltech Research Tokamak", "author": [ { "family_name": "Hedemann", "given_name": "Mark Allen", "clpid": "Hedemann-Mark-Allen" } ], "thesis_advisor": [ { "family_name": "Gould", "given_name": "Roy Walter", "clpid": "Gould-R-W" } ], "thesis_committee": [ { "family_name": "Gould", "given_name": "Roy Walter", "clpid": "Gould-R-W" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Saffman", "given_name": "Philip G.", "clpid": "Saffman-P-G" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "An experimental investigation of magnetic field fluctuations in a research tokamak plasma has been performed. The fluctuations were measured with movable probes inserted directly into the plasma. Estimates of the fluctuating field strength, power spectral density, and correlation lengths have been made by calculations on the raw data. The fluctuations were found to be of comparable strength for the radial and poloidal components, while the toroidal component was found to be at least a factor of 5 weaker in strength. The fluctuating field strength showed no apparent dependence on plasma current and safety factor at the edge, but increased with electron density during gas puffing and as the minor radius of measurement was decreased.
\r\n\r\nThe power spectral density indicated that the fluctuations could be divided into two frequency regions. The low frequency region (f < 100 kHz) was dominated by coherent MHD modes with correlation lengths on the order of the tokamak size. The high frequency (f > 100 kHz) region appeared to be turbulent in nature with short correlation lengths in the poloidal direction (< .01 m), but longer correlation lengths in the radial direction (> .04 m). The high frequency region showed a roll-off in frequency of \u03b4Br of approximately f-2.5.
\r\n\r\nThe results are compared with theories of fluctuation sources and the effects of fluctuations on anomalous electron thermal transport. The best fit to the high frequency region spectral density is given by a statistical theory of fluctuations. The fluctuating field strength appears to be more than an order of magnitude too small to account for the anomalous electron thermal transport using stochastic field theory.
", "doi": "10.7907/z70q-f715", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:6066", "collection": "thesis", "collection_id": "6066", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09282010-100527331", "primary_object_url": { "basename": "Gabriel_ak_1981.pdf", "content": "final", "filesize": 5260594, "license": "other", "mime_type": "application/pdf", "url": "/6066/1/Gabriel_ak_1981.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Optogalvanic Spectroscopy and Cataphoretic Laser Isotope Separation", "author": [ { "family_name": "Gabriel", "given_name": "Andrew Keith", "clpid": "Gabriel-Andrew-Keith" } ], "thesis_advisor": [ { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" } ], "thesis_committee": [ { "family_name": "Shair", "given_name": "Fredrick H.", "clpid": "Shair-F-H" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Bellan", "given_name": "Paul Murray", "orcid": "0000-0002-0886-8782", "clpid": "Bellan-P-M" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A microscopic theory for the positive column discharge (PCD) is developed using rate equations and power balance equations to model the microscopic discharge processes. Macroscopic variables are calculated from the microscopic parameters. The model is used to characterize a hydrogen-helium PCD.
\r\n\r\nThe equations in the model are modified to account for the presence of resonant (H-alpha) radiation from an external source. The model is then used to predict the voltage change in a hydrogen PCD (the optogalvanic effect) as a function of current, illumination intensity, and gas pressure. The results compare very favorably with experiments conducted to measure the OGE.
\r\n\r\nTransient voltage changes induced by resonant illumination in a PCD are calculated by numerical integration of the model equations. Perturbation theory is applied to the equations to obtain more physical insight into the physics of the transient OGE.
\r\n\r\nThe experimental apparatus used to measure the OGE and that used to measure the electron temperature (double probes) are described. A discussion of experimental problems covers some of the difficulties encountered.
\r\n\r\nThe PCD model and OGE model are used to evaluate the practicality of separating hydrogen and deuterium by optically assisted cataphoresis in the PCD.
\r\n\r\nThe possibility that recombination is a dominant process in the discharge is discussed in detail and rejected.
\r\n\r\nA careful description of the interaction of the illuminating radiation and the PCD plasma is given, with special attention to homogeneous and inhomogeneous broadening processes, saturation of absorption and saturation of the OGE, and the relative bandwidths of the illuminating radiation and discharge gas.
\r\n\r\nSome suggestions are made for future work.
", "doi": "10.7907/xhjf-aa40", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:3918", "collection": "thesis", "collection_id": "3918", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10042006-111807", "type": "thesis", "title": "Ultra-High Frequency Dynamics of Semiconductor Injection Lasers", "author": [ { "family_name": "Lau", "given_name": "Kam-Yin", "clpid": "Lau-Kam-Yin" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Walker", "given_name": "Robert Lee", "clpid": "Walker-R-L" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "Caltech Distinguished Alumni Award" }, { "literal": "div_eng" } ], "abstract": "Experimental and theoretical studies on the high frequency dynamics of (GaAl)As semiconductor lasers center on three main areas: 1) analog modulation response of laser diodes; 2) pulse (pulse code modulation) response of laser diodes and 3) generation and quenching of intensity pulsations in laser diodes coupled to external cavities.
\r\n\r\nThe basic analog modulation and transient characteristics of injection lasers with various structures are studied and compared. The basic limitations on ultrahigh frequency ( > 5GHz) modulation of lasers are considered. Self-pulsations in injection lasers are studied and their interaction with external cavities are clarified. These studies lead to the quenching of self-pulsation and ultra-short short pulse generation in laser diodes by coupling to an external cavity. A novel external fiber resonator is introduced for this purpose. Pattern effects in pulse code modulation of injection lasers are studied and a bipolar pulsing scheme devoid of the above effect is described. The transverse mode shift in a transverse junction laser under ultrashort electrical pulse excitation is investigated. Finally, the frequency response of superluminescent lasers (lasers without mirrors) is analysed.
\r\n", "doi": "10.7907/f057-zj77", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:3621", "collection": "thesis", "collection_id": "3621", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09182006-141505", "type": "thesis", "title": "(AlGa)As Semiconductor Lasers and Integrated Optoelectronics", "author": [ { "family_name": "Wilt", "given_name": "Daniel Paul", "clpid": "Wilt-Daniel-Paul" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Five subjects related to monolithic integration of electronic and optical devices in the (AlGa)As material system are treated in this thesis. They are:
\r\n\r\n1. The Integrated Optoelectronic Repeater:
\r\n\r\nThe design, fabrication, and testing of the first monolithic integrated optical repeater is described. This device consists of an optical detector, electronic gain stage, and current modulated semiconductor laser transmitter integrated in a single crystal chip to perform the function of regenerating an optical signal as might be found in an optical communication system. The device has a measured optical gain (light out to light in) of 10 dB.
\r\n\r\n2. Ion Implanted Lasers and Schottky Gate Field Effect Transistors:
\r\n\r\nThe use of ion implantation as a technique to fabricate both lasers and field effect transistors is described. Devices fabricated include a beryllium implanted laser diode on N type GaAs substrate, a beryllium implanted laser diode on semi-insulating Cr doped GaAs substrate integrated with a field effect transistor driver, and sulfur implanted GaAs field effect transistors.
\r\n\r\n3. A Steady State Lateral Model of the Double Heterostructure Laser:
\r\n\r\nA theoretical model of the double heterostructure laser is described which treats the p-n junction in the device correctly by using fundamental semiconductor relationships and reasonable assumptions about the device heterointerfaces. The model treats both the electronic and optical properties self consistently, making the model valid above lasing threshold. Finite element formalism is adopted as a solution technique to enable the treatment of complicated diode geometries. An example is treated and theoretical and experimental results are compared.
\r\n\r\n4. The Effect of Lateral Carrier Diffusion on the Modulation Response of a Semiconductor Laser:
\r\n\r\nThe effect of lateral carrier diffusion upon the modulation characteristics of the semiconductor laser is investigated. A self consistent analysis of the spatially dependent rate equations is performed using a finite element model. The transverse junction stripe laser is treated as an example and a comparison is made between lateral carrier diffusion and spontaneous emission as damping mechanisms for the resonance peak. Experimental results bear out the conclusion that the relaxation resonance in this device is damped mainly by lateral carrier diffusion. In addition, a simple analytic result is presented which illustrates qualitatively the effect of lateral carrier diffusion upon such devices. The conclusion from this result is that lateral carrier diffusion serves to damp the relaxation resonance in the semiconductor laser quite well, but probably will not serve to improve the upper limit on modulation frequency as might have been suspected.
\r\n\r\n5. Effective Permittivity Formalism and the Design of Buried Heterostructure Lasers:
\r\n\r\nAn approach to effective permittivity formalism is presented which clarifies and extends the use of this technique particularly in the treatment of waveguiding in the semiconductor laser. The scalar wave equation is posed in a variational form, and the effective permittivity formalism is treated as a variational approximation technique. This approach shows clearly the nature and limits of the approximation involved. The formalism is applied to the case of the buried heterostructure laser and the results differ considerably from the conventional application of effective permittivity formalism to this device when a reasonable form is assumed for the variational modal profile.
", "doi": "10.7907/f9jz-ez68", "publication_date": "1981", "thesis_type": "phd", "thesis_year": "1981" }, { "id": "thesis:5152", "collection": "thesis", "collection_id": "5152", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12282005-104818", "primary_object_url": { "basename": "Agmon_p_1980.pdf", "content": "final", "filesize": 7619516, "license": "other", "mime_type": "application/pdf", "url": "/5152/1/Agmon_p_1980.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "I. Design, Control, and Characterization of the Passively Mode Locked CW Dye Laser. II. Photoconductive Impulse Response and Excess Carrier Lifetime of Cr-doped GaAs", "author": [ { "family_name": "Agmon", "given_name": "Pinchas", "clpid": "Agmon-Pinchas" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" }, { "family_name": "Smith", "given_name": "Darryl L.", "clpid": "Smith-D-L" }, { "family_name": "Culick", "given_name": "Fred E. C.", "clpid": "Culick-F-E-C" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis consists of two parts. The subject of the first part is the design, control, and characterization of the passively mode locked CW dye laser, which is capable of producing a stable continuous train of subpicosecond pulses. Following a description of the laser's elements, the mode stability of its multi-mirror resonator is studied. The monitoring of the laser operational state by pulsewidth and bandwidth measurements is described.
\r\n\r\nIn the second part, the photoconductive impulse response and excess carrier lifetime of semi-insulating Cr:GaAs is studied experimentally and analytically. In the transient photoconductive experiment, the material is irradiated with a continuous train of picosecond light pulses with photon energy above the band-gap energy, generated by the passively mode locked CW dye laser described in part I. A photoconductive decay time of 67 psec is deduced from the observations and interpreted as the result of both bulk and surface recombination. It is shown that it agrees well with longer carrier lifetime in Cr:GaAs measured under steady state conditions with longer illumination wavelengths.
", "doi": "10.7907/hr51-0r95", "publication_date": "1980", "thesis_type": "phd", "thesis_year": "1980" }, { "id": "thesis:6849", "collection": "thesis", "collection_id": "6849", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03122012-112325331", "primary_object_url": { "basename": "Mickelson_ar_1978.pdf", "content": "final", "filesize": 19758696, "license": "other", "mime_type": "application/pdf", "url": "/6849/1/Mickelson_ar_1978.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Electromagnetic Wave Propagation in Almost Periodic Media", "author": [ { "family_name": "Mickelson", "given_name": "Alan Rolf", "orcid": "0000-0003-2529-8301", "clpid": "Mickelson-Alan-Rolf" } ], "thesis_advisor": [ { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" } ], "thesis_committee": [ { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "family_name": "Langmuir", "given_name": "Robert V.", "clpid": "Langmuir-R-V" }, { "family_name": "Keller", "given_name": "Herbert Bishop", "clpid": "Keller-H-B" }, { "family_name": "Bridges", "given_name": "William B.", "clpid": "Bridges-W-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The problem of electromagnetic wave propagation in almost periodic\r\nmedia is investigated and a solution is obtained directly from Maxwell's\r\nequations. Techniques to evaluate this solution are developed. These\r\ntechniques involve a generalization to almost periodic media of the\r\nBrillouin diagram of periodic media. The method of invariant imbedding\r\nis applied to the coupled mode equations which determine the Brillouin\r\ndiagram for the purpose of transforming them to coupled Riccati equations.\r\nThese coupled Riccati equations, when subjected to a single boundary condition,\r\ndetermine the solutions to both the periodic and almost periodic\r\nboundary value problems. These evaluation techniques are used to place\r\nin evidence similarities and differences of wave propagation in periodic\r\nand almost periodic media. It is shown that although the periodic and\r\nalmost periodic theories agree in many cases of interest, there exist\r\ncases in which distinct differences appear. In cases of multi-tone perturbations,\r\nthe almost periodic theory yields both simpler and more reasonable\r\nresults than the periodic theory.", "doi": "10.7907/SZMY-A964", "publication_date": "1978", "thesis_type": "phd", "thesis_year": "1978" } ]