Microfluidics is a multidisciplinary field that uses minute volumes of liquids to attempt complex functionalities. These complicated functionalities often require manipulating interfaces through external forces. In addition, optics have become a fundamental necessity for most microfluidic devices. We combine these two concepts and call it surface optofluidics. Here, we focus on the advantages of surface optofluidics for the development of a biosensor, specifically focusing on the flexibility and adaptability offered by these techniques.
\r\n\r\nTo introduce the advantages presented by surface optofluidics, devices using droplet electrowetting techniques are discussed. We then discuss biosensing through structured electrodes on surfaces. The electrodes are used to align asymmetric bacteria. The aligned bacteria are detected optically. This method of detection is improved by incorporating two different surface optofluidic methods. Concentration and motion control of the bacterium is demonstrated with electric fields on three dimensionally structured electrodes and an optothermal nanoparticle carpet. Finally, we show preliminary work in the study of single bacterium behavior using nanoparticles as labels to detect its specific alignment in space.
\r\n", "doi": "10.7907/KYZG-3503", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6281", "collection": "thesis", "collection_id": "6281", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04082011-064907780", "primary_object_url": { "basename": "HSIEH_PhD_thesis_2011.pdf", "content": "final", "filesize": 5320736, "license": "other", "mime_type": "application/pdf", "url": "/6281/1/HSIEH_PhD_thesis_2011.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Imaging with Second-Harmonic Generation Nanoparticles", "author": [ { "family_name": "Hsieh", "given_name": "Chia-Lung", "clpid": "Hsieh-Chia-Lung" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Daraio", "given_name": "Chiara", "clpid": "Daraio-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Second-harmonic generation nanoparticles show promise as imaging probes due to their coherent and stable signal with a broad flexibility in the choice of excitation wavelength. In this thesis, we developed and demonstrated barium titanate nanoparticles as second-harmonic radiation imaging probes. We studied the absolute second-harmonic generation efficiency of the nanoparticles on single-particle level. The polarization dependent second-harmonic signal of single nanoparticles was studied in detail. From the measured polar response, we were able to find the orientation of the nanoparticle. We developed a biochemical interface for using the second-harmonic nanoprobes as biomarkers, including in vitro cellular imaging and in vivo live animal imaging. The nanoparticles were surface functionalized with primary amine groups for stable colloidal dispersion. We achieved specific labeling of the second-harmonic nanoprobes via immunostaining where the antibodies were covalently conjugated onto the nanoparticles. We observed no toxicity of the functionalized nanoparticles to biological cells. The coherent second-harmonic signal radiated from the nanoparticles offers opportunities for new imaging techniques. Using interferometric detection, namely harmonic holography, both amplitude and phase of the second-harmonic field can be captured. Through digital beam propagation, three-dimensional field distribution, reflecting three-dimensional distribution of the nanoparticles, can be reconstructed. We achieved a scan-free three-dimensional imaging of nanoparticles in biological cells with sub-micron spatial resolution by using the harmonic holographic microscope. We further exploited the coherent second-harmonic signal for imaging through scattering media by performing optical phase conjugation of the second-harmonic signal. We demonstrated an all-digital optical phase conjugation of the second-harmonic signal originated from a nanoparticle by combining harmonic holography and dynamic computer generated holography using a spatial light modulator. The phase-conjugated second-harmonic scattered field retraced the scattering trajectory and formed a clean focus on the nanoparticle placed inside a scattering medium. The nanoparticle acted as a beacon of light; it helped us find the tailored wavefront for concentrating light at the nanoparticle inside the scattering medium. We also demonstrated imaging through a thin scattering medium by raster-scanning the phase-conjugated focus in the vicinity of the beacon nanoparticle, in which a clear image of a target placed behind a ground glass diffuser was obtained.", "doi": "10.7907/WCS2-FD82", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:1719", "collection": "thesis", "collection_id": "1719", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05102009-103332", "type": "thesis", "title": "Plasmonic Nanoparticles for Optofluidic Applications", "author": [ { "family_name": "Adleman", "given_name": "James Richard", "clpid": "Adleman-James-Richard" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Erickson", "given_name": "David", "clpid": "Erickson-D" }, { "family_name": "Goodwin", "given_name": "David G.", "clpid": "Goodwin-D-G" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis discusses the application of colloidal particles to optofluidic systems. Colloidal particles can be added as a \"dopant\" to the liquids in these devices to provide functionality that cannot be obtained with homogenous fluids. We examine electrooptic effects in liquid suspensions asymmetric metallic nanoparticles. The theoretical optical properties of gold nanorods and noble metal nanohalfshells are computed and compared with those of actual colloidal dispersions. We discuss the design and fabrication of electro-optic waveguides utilizing these suspensions as the active material. We also study the dynamics of photothermal holograms recorded by nanosecond laser pulses in suspensions of silver nanospheres. Unexpected transients in the grating diffraction efficiency correspond to the nanoscale inhomgeneity of the colloid. Longer timescale decay can be used to measure the thermal conductivity of the liquid as predicted by the established theory of heat conduction. This technique is extended to perform spatial imaging of the thermal diffusivity of immiscible binary liquids. Gold nanosphere coated substrates for microfluidic devices are employed to enable optical actuation of fluids. Nanoparticle absorption of continuous wave laser light was used to trap air bubbles inside partially filled microfluidic channels. Light focused on the array near one side of the trapped bubble will drive a mass flow across the bubble. This evaporative bubble assisted mass transport mechanism can be operated as a pump powered by a stationary laser beam. In addition, the process efficiently separates volatile and non-volatile materials and can concentrate and purify specimens in solution.
\r\n\r\nFinally, several schemes for storing and extracting data from subwavelength volumes using spectral multiplexing of semiconductor quantum dots are explored. We demonstrate microfluidic composition and delivery of cocktails of several colors of quantum dots to act as information packets for optical storage. In addition we analyze imaging at the subwavelength level using a patterned surface of quantum dots. The theoretical performance of such a surface is compared to imaging through nanoapertures as is currently implemented in optofluidic microscopy.
\r\n", "doi": "10.7907/QB6E-2Q64", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:5251", "collection": "thesis", "collection_id": "5251", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09142007-143251", "primary_object_url": { "basename": "thesis_zhenyu.pdf", "content": "final", "filesize": 12717987, "license": "other", "mime_type": "application/pdf", "url": "/5251/1/thesis_zhenyu.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optofluidic Dye Lasers", "author": [ { "family_name": "Li", "given_name": "Zhenyu", "orcid": "0000-0002-7752-6225", "clpid": "Li-Zhenyu" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Libbrecht", "given_name": "Kenneth George", "clpid": "Libbrecht-K-G" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optofluidic dye lasers refer to a class of liquid dye lasers, usually on a microfabricated device, in which the adaptive nature of the liquid gain medium allows the dynamical control of the laser properties. Miniaturizing liquid dye lasers onto a microfluidic device not only results in compact, easy-to-maintain and safe dye laser systems, but also provides unprecedented optical performances such as precise spatial mode control, low threshold, and automatic fluidic tuning. Equally important, such on-chip liquid laser sources represent an important component for \"lab-on-a-chip\" systems.
\r\n\r\nThis thesis studies the implementations of optofluidic dye lasers on polydimethylsiloxane (PDMS) based microfluidic devices. Replica molding soft lithography was used to fabricate monolithic PDMS devices which contain both wavelength-scale optical structures and large-sized microfluidic channels. We have demonstrated narrow linewidth single mode DFB lasers, simultaneous operation of integrated DFB laser arrays with a single pump, multiple color lasing from the same DFB cavity, continuous mechanical wavelength tuning over a 60nm range, microfluidic wavelength tuning, single mode liquid-core microring lasers using Vernier effect, liquid-cladding evanescent gain DFB lasers, and monolithic integration with PDMS microfluidic circuits. Typical laser thresholds achieved are well within the reach of commercial high power laser diodes, thus enabling the implementations of compact tunable laser sources for portable \u201clab-on-a-chip\u201d devices. The impressive performances, diverse geometries and applications clearly demonstrate the power of optofluidic integration and adaptation.
\r\n\r\n", "doi": "10.7907/AQQR-QG80", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:5057", "collection": "thesis", "collection_id": "5057", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12182007-163333", "primary_object_url": { "basename": "Thesis_v2_combined_new_v2.pdf", "content": "final", "filesize": 4563403, "license": "other", "mime_type": "application/pdf", "url": "/5057/1/Thesis_v2_combined_new_v2.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optofluidic Microscopy: Technology Development and Its Applications in Biology", "author": [ { "family_name": "Heng", "given_name": "Xin", "clpid": "Heng-Xin" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Sternberg", "given_name": "Paul W.", "orcid": "0000-0002-7699-0173", "clpid": "Sternberg-P-W" }, { "family_name": "Troian", "given_name": "Sandra M.", "orcid": "0000-0003-1224-6377", "clpid": "Troian-S-M" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The Optofluidic Microscope (OFM) is a new imaging platform based upon nanoapertures that are fabricated on planar metallic film, whilst microfluidic delivery technology is used to transport the objects-of-interest. The planar nature of OFM makes it ideal to integrate with other micro total analysis systems, such as cell sorters or cell culturing chambers. Furthermore, a variety of imaging functionalities, such as differential phase contrast, fluorescence, and Raman spectroscopy can potentially fit into a single OFM device.
\r\n\r\nThis thesis reports on the early technology development of Optofluidic Microscopy. I have built a variety of off-chip prototypes of OFM that all possess different functionalities. These OFM prototypes include 1D array OFM, hydraulically pumped OFM, 2D nanoaperture grid OFM, super high-resolution OFM, OFM coupled with optical tweezer actuation, fluorescent OFM, electrokinetic enabled OFM, etc.
\r\n\r\nI applied the first OFM prototype in imaging Caenorhabditis elegans (C. elegans) larvae and characterizing different genotypes. Later on, the microscopy properties of OFM, such as the optical resolution and the depth of field, were thoroughly investigated both experimentally and theoretically. More recently, I successfully combined optical tweezers with a grid-based OFM prototype, which was then used in high-resolution imaging of microspheres and a few biological samples. In addition, preliminary results on fluorescence OFM imaging were also demonstrated.
\r\n\r\nI trust that these functionalities, after being demonstrated off-chip, can be readily fabricated and then assembled as a complete on-chip OFM. It will eventually enable a real \"microscale microscope on a chip\".
\r\n", "doi": "10.7907/JAYF-RX26", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:3011", "collection": "thesis", "collection_id": "3011", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08042006-144107", "primary_object_url": { "basename": "Thesis_Ehsan.pdf", "content": "final", "filesize": 30587538, "license": "other", "mime_type": "application/pdf", "url": "/3011/1/Thesis_Ehsan.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optotronics: Optically Inspired Electronics", "author": [ { "family_name": "Afshari", "given_name": "Ehsan", "orcid": "0000-0002-4528-1788", "clpid": "Afshari-Ehsan" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Marsden", "given_name": "Jerrold E.", "clpid": "Marsden-J-E" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Waves are everywhere, from the distribution of cars on a highway to the wave patterns in the ocean. Intriguing phenomena in wave propagation, such as Soliton resonance, kink-antikink interaction, self-focusing, and Peakon generation can be used in many practical applications leading to novel architectures for signal processing and generation. These E/M based approaches could be particularly useful in the case of Extremely Wide Band (EWB) (DC to more than 100GHz) circuits and systems where the limited transistor cut-off frequency, maximum power efficiency, and breakdown voltage pose serious constraints on the use of conventional circuit techniques.
\r\n\r\nTo overcome the limitations of active devices in EWB signal processing and generation, we propose a general class of solutions based on novel circuit topologies inspired by commonly used structures in electromagnetics, and more specifically optics. The proposed methodology is based on nonlinear and/or inhomogeneous one-dimensional (1D) transmission lines which we have successfully extended to two-dimensional transmission lattices. The principles behind these designs stem from the mathematical theory of linear and nonlinear wave propagation. By analyzing the models for the transmission lines/lattices, we are able to exploit the large body of theory to design circuits, demonstrating the narrowest reported pulse on silicon (2.5ps), and for a single integrated-circuit silicon-based amplifier, the highest achieved center frequency of operation (85GHz) and the highest achieved power output (120mW) at this frequency. In addition, we have reported the first in-silicon transmission line system capable of sharpening both rising and falling edges of NRZ data by increasing the bandwidth. In the end, we will also present how the same approach can be applied to realize ultra-fast computation systems (such as a sub-nanosecond Fourier and Hankel transformers in silicon) and other structures, leading to a new design discipline we like to call \"Optotronics\".
\r\n", "doi": "10.7907/Z95M63XK", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:5201", "collection": "thesis", "collection_id": "5201", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05252007-220130", "primary_object_url": { "basename": "PhDThesisSiyangZheng.pdf", "content": "final", "filesize": 15402284, "license": "other", "mime_type": "application/pdf", "url": "/5201/1/PhDThesisSiyangZheng.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "On-Chip Blood Count", "author": [ { "family_name": "Zheng", "given_name": "Siyang", "orcid": "0000-0002-0616-030X", "clpid": "Zheng-Siyang" } ], "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": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Kasdan", "given_name": "Harvey L.", "clpid": "Kasdan-H-L" }, { "family_name": "Gharib", "given_name": "Morteza", "orcid": "0000-0003-0754-4193", "clpid": "Gharib-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Blood count is one of the most common medical laboratory tests performed today. It provides information on patient\u2019s oxygen carrying capacity, immune system functionality, and the overall hemapoiesis process for disease diagnosis and drug side-effect monitoring. Traditionally blood count is performed either manually or by conventional automated blood analyzers. With the advance of microfabrication, on-chip blood count has become a target for miniaturization aiming at providing cost-effective, functional, capable point-of-care devices and systems that use less than 100 nL of blood sample and generate measurement results within minutes. The focus of this thesis is on investigation of erythrocyte/leukocyte counting and leukocyte differential, which are the two key components in blood count, in microdevices.
\r\n\r\nDue to the large number ratio of erythrocytes to leukocytes and their property overlap, conventional automated blood analyzers accomplish blood count in several different channels by measuring different parameters. Similarly, in microdevices, it is desirable that erythrocytes and leukocytes can be separated before further analysis. Two types of hydrodynamic separation devices were investigated to continuously separate erythrocytes and leukocytes based on size. The principle of the device exploits the laminar flow in microdevices and design of streamlines which particles follow. Pillar-shaped devices with single geometrical design demonstrate a binary separation profile. With proper design, separation efficiency over 90% can be achieved. Channel-shaped devices, an improved design, can achieve similar separation efficiency with the added benefits of a smaller footprint, fewer requirements on flow control, and easier integration with downstream components.
\r\n\r\nErythrocyte and leukocyte count is accomplished with electrical impedance sensing, which is one of the most accurate ways to measure particle volume. The well-known problem of small double-layer capacitance inherent to micro impedance sensors is solved by two methods: platinum black electroplating on the electrode surface and inductor-induced resonance sensing. In the first method, platinum black is electroplated in situ on the electrode surfaces, which increases the effective surface area by two orders of magnitude and thus increases the double-layer capacitance significantly. The other innovative way, inductor-induced resonance sensing, nullifies the capacitive components in the system at the resonance frequency by connecting a parallel inductor to the system. In this way the sensitivity can be greatly improved and the optimal sensing frequency can be chosen from the inductance value. For both methods, polystyrene beads of different diameters were used for validation, while diluted blood samples and leukocyte-rich plasma were used to successfully demonstrate the feasibility.
\r\n\r\nTwo-part leukocyte differential is demonstrated in microflow cytometers with fluorescence sensing. Unlike methods used in conventional blood analyzers, undiluted blood samples are stained with nucleic acid stain acridine orange. Lymphocytes and granulocytes emit fluorescent light at different peak frequency after interaction with the dye due to the difference in cellular composition. Using the undiluted sample greatly minimizes sample preparation procedure, and reduces the overall measurement time, the reagent, and the waste volume. These benefits make it a practical method for implementation in microdevices. A throughput of one thousand leukocytes per second was demonstrated, which means the leukocyte differential could be accomplished in a couple of seconds.
", "doi": "10.7907/SJ43-XM11", "publication_date": "2007", "thesis_type": "phd", "thesis_year": "2007" }, { "id": "thesis:1408", "collection": "thesis", "collection_id": "1408", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04182006-162552", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 7175762, "license": "other", "mime_type": "application/pdf", "url": "/1408/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Temperature-Controlled Microchip Liquid Chromatography System", "author": [ { "family_name": "Shih", "given_name": "Victor-Chi-Yuan", "clpid": "Shih-Victor-Chi-Yuan" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" }, { "family_name": "Lee", "given_name": "Terry D.", "clpid": "Lee-T-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "High-performance liquid chromatography (HPLC) is one of the most important analytical tools heavily used in the fields of chemistry, biotechnology, pharmaceutics, and the food industry. The power of liquid chromatography comes from its ability to achieve molecular separation with extremely high efficiency and its great flexibility of incorporating versatile sensors for detecting a broad range of analytes. In the past decades, great efforts have been put into liquid chromatography instrumentation and methods, aiming to further improve separation efficiency, sensitivity, repeatability, throughput, and costs. The contribution of this thesis is to illustrate with real examples the great potential of MEMS microchip liquid chromatography systems with on-chip temperature control for replacing and improving the conventional desktop HPLC systems.
\r\n\r\nThis thesis is composed of seven chapters. Chapter 1 gives an introduction to MEMS technology and its application in making lab-on-a-chip systems. Chapter 2 describes the theoretical background and the evolution of HPLC technology. Chapter 3 demonstrates how to use state-of-the-art MEMS technology to make high-pressure microfluidic channels, which will be used for constructing microchip HPLC systems later. Chapter 4 describes a temperature-controlled microchip HPLC system that uses a temporal temperature gradient to achieve analyte elution. Separation of amino acids and low density lipoproteins was successfully demonstrated using the proposed system. Chapter 5 describes a novel embedded HPLC system, which demonstrated a record high pressure capacity (> 1000 psi) among microchip HPLC systems. High quality separation results of trace-level daunorubicin and doxorubicin were obtained using the proposed system and laser-induced fluorescence detection. A novel C4D sensor together with the RISE sensitivity enhancement method was proposed and investigated for the first time for microchip HPLC analyte detection. Chapter 6 describes the first work to pack 30 nm gold nanoparticles into the HPLC separation column as the stationary phase with the assistance of in-situ molecular self-assembly between nanoparticles and thiolated molecules. Preliminary results demonstrated the possibility of building fully filled nanoparticle HPLC columns for extremely high separation efficiency application. Chapter 7 then gives the conclusions of this thesis.
", "doi": "10.7907/ZDK5-Q871", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:895", "collection": "thesis", "collection_id": "895", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03072006-135433", "primary_object_url": { "basename": "00_DirkWalther_PhDthesis.pdf", "content": "final", "filesize": 6400488, "license": "other", "mime_type": "application/pdf", "url": "/895/1/00_DirkWalther_PhDthesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Interactions of Visual Attention and Object Recognition: Computational Modeling, Algorithms, and Psychophysics", "author": [ { "family_name": "Walther", "given_name": "Dirk", "orcid": "0000-0001-8585-9858", "clpid": "Walther-Dirk" } ], "thesis_advisor": [ { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" } ], "thesis_committee": [ { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Itti", "given_name": "Laurent", "clpid": "Itti-L" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Andersen", "given_name": "Richard A.", "orcid": "0000-0002-7947-0472", "clpid": "Andersen-R-A" }, { "family_name": "Shimojo", "given_name": "Shinsuke", "orcid": "0000-0002-1290-5232", "clpid": "Shimojo-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Selective visual attention provides an effective mechanism to serialize perception of complex scenes in both biological and machine vision systems. In extension of previous models of saliency-based visual attention by Koch and Ullman (Human Neurobiology, 4:219-227, 1985) and Itti et al. (IEEE PAMI, 20(11):1254-1259, 1998), we have developed a new model of bottom-up salient region selection, which estimates the approximate extent of attended proto-objects in a biologically realistic manner.
\r\n\r\nBased on our model, we simulate the deployment of spatial attention in a biologically realistic model of object recognition in the cortex and find, in agreement with electrophysiology in macaque monkeys, that modulation of neural activity by as little as 20 % suffices to enable successive detection of multiple objects.
\r\n\r\nWe further show successful applications of the selective attention system to machine vision problems. We show that attentional grouping based on bottom-up processes enables successive learning and recognition of multiple objects in cluttered natural scenes. We also demonstrate that pre-selection of potential targets decreases the complexity of multiple target tracking in an application to detection and tracking of low-contrast marine animals in underwater video data.
\r\n\r\nA given task will affect visual perception through top-down attention processes. Frequently, a task implies attention to particular objects or object categories. Finding suitable features can be interpreted as an inversion of object detection. Where object detection entails mapping from a set of sufficiently complex features to an abstract object representation, finding features for top-down attention requires the reverse of this mapping. We demonstrate a computer simulation of this mechanism with the example of top-down attention to faces.
\r\n\r\nDeploying top-down attention to the visual hierarchy comes at a cost in reaction time in fast detection tasks. We use a task switching paradigm to compare task switches that do with those that do not require re-deployment of top-down attention and find a cost of 20-28 ms in reaction time for shifting attention from one stimulus attribute (image content) to another (color of frame).
", "doi": "10.7907/P5NY-VC91", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:2061", "collection": "thesis", "collection_id": "2061", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05252006-221314", "primary_object_url": { "basename": "MichelaMunozTH.pdf", "content": "final", "filesize": 4113829, "license": "other", "mime_type": "application/pdf", "url": "/2061/1/MichelaMunozTH.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Coherent Optical Array Receiver for PPM Signals Under Atmospheric Turbulence", "author": [ { "family_name": "Mu\u00f1oz Fern\u00e1ndez", "given_name": "Michela", "orcid": "0000-0001-8028-2156", "clpid": "Mu\u00f1oz-Fern\u00e1ndez-M" } ], "thesis_advisor": [ { "family_name": "Hassibi", "given_name": "Babak", "clpid": "Hassibi-B" } ], "thesis_committee": [ { "family_name": "Hassibi", "given_name": "Babak", "clpid": "Hassibi-B" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Elachi", "given_name": "Charles", "clpid": "Elachi-C" }, { "family_name": "Mabuchi", "given_name": "Hideo", "clpid": "Mabuchi-H" }, { "family_name": "Mukai", "given_name": "Ryan", "clpid": "Mukai-R" }, { "family_name": "Vilnrotter", "given_name": "Victor", "clpid": "Vilnrotter-V" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The performance of a coherent free-space optical communications system operating in the presence of turbulence is investigated. Maximum Likelihood Detection techniques are employed to optimally detect Pulse Position Modulated signals with a focal-plane detector array and to reconstruct the turbulence-degraded signals.
\r\n\r\nLaboratory equipment and experimental setup used to carry out these experiments at the Jet Propulsion Laboratory are described. The key components include two lasers operating at 1064 nm wavelength for use with coherent detection, a 16 element (4 X 4) InGaAs focal-plane detector array, and a data-acquisition and signal-processing assembly needed to sample and collect the data and analyze the results. The detected signals are combined using the least-mean-square (LMS) algorithm. In the first part of the experimental results we show convergence of the algorithm for experimentally obtained signal tones in the presence of atmospheric turbulence. The second part of the experimental results shows adaptive combining of experimentally obtained heterodyned pulse position modulated (PPM) signals with pulse-to-pulse coherence in the presence of simulated spatial distortions resembling atmospheric turbulence. The adaptively combined PPM signals are phased up via an LMS algorithm suitably optimized to operate with PPM in the presence of additive shot noise. A convergence analysis of the algorithm is presented, and results with both computer-simulated and experimentally obtained PPM signals are analyzed.
\r\n\r\nThe third part of the experimental results, in which the main goal of this thesis is achieved, includes an investigation of the performance of the Coherent Optical Receiver Experiment (CORE) at JPL. Bit Error Rate (BER) results are presented for single and multichannel optical receivers where quasi shot noise-limited performance is achieved under simulated turbulence conditions using noncoherent postdetection processing techniques. Theoretical BER expressions are compared with experimentally obtained BER results, and array combining gains are presented. BER results are shown as a function of signal-to-noise ratio (SNR), photons per symbol, and photons per bit (PPB).
", "doi": "10.7907/VDSA-SA42", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:4639", "collection": "thesis", "collection_id": "4639", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11222005-163249", "primary_object_url": { "basename": "thesis.PDF", "content": "final", "filesize": 39143278, "license": "other", "mime_type": "application/pdf", "url": "/4639/6/thesis.PDF", "version": "v4.0.0" }, "type": "thesis", "title": "Fluidic and Polymeric Integration and Functionalization of Optical Microresonators", "author": [ { "family_name": "Maune", "given_name": "Brett Michael", "clpid": "Maune-Brett-Michael" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical resonators are structures that spatially confine and temporally store light. The use of such resonators continues to permeate throughout society as improvements in their design and fabrication qualify them to fulfill an ever-increasing array of technological and scientific applications. Traditionally, resonators have primarily been used in lasers and as filters, and more recently have been utilized in other areas including chemical sensing, spontaneous emission modulation, and quantum electrodynamics experiments. In many of these applications, the functionalities of the resonators are solely derived from the geometry and material composition of the resonators themselves. The central theme of this thesis is the investigation of further increasing a resonator's functionality through its integration with fluidic and polymeric materials.
\r\n\r\nThe thesis begins with an investigation of integrating silicon ring resonators with electro-optic polymer and liquid crystal in an effort to tune the resonators' resonant wavelengths. Although the electro-optic polymer efforts are a failure, we are able to electrically tune the rings' resonances using electrodes and the reorientation of liquid crystal surrounding the resonators. We then take the knowledge and experience acquired from these experiments and pursue the functionalization of photonic crystal laser resonators, a relatively new class of microresonators constructed from a thin slab of InGaAsP quantum well material with a periodic array of holes etched through the slab. To this end, we first infiltrate the porous resonators with liquid crystal and construct liquid crystal cells around the devices. We are then able to tune the lasing wavelengths by reorienting the liquid crystal with a voltage applied across the cell. Next, we devise a new photonic crystal cavity designed to optimally interact with infiltrated birefringent materials, by supporting two orthogonally polarized high-Q modes. Again, we infiltrate the cavity with liquid crystal, but this time optically control the liquid crystal orientation with a photoaddressable polymer film. By doing so we are able to realize a fundamentally new laser tuning method by reversibly Q-switching a resonator's lasing mode between the two cavity modes and thereby control the laser's emission wavelength and polarization. The successful fluidic and polymeric integration with optical resonators presented in this thesis demonstrates some of the possible synergies that can be obtained with such integration and suggests that further enhancements in resonator functionality is possible.
", "doi": "10.7907/2746-3104", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:4457", "collection": "thesis", "collection_id": "4457", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11082005-204747", "primary_object_url": { "basename": "Title.pdf", "content": "final", "filesize": 26939, "license": "other", "mime_type": "application/pdf", "url": "/4457/3/Title.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "High-Q Microcavities: Optomechanical Nonlinearities, Measurement Techniques and Applications", "author": [ { "family_name": "Rokhsari Azar", "given_name": "Hossein", "clpid": "Rokhsari-Azar-Hossein" } ], "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": "Crosignani", "given_name": "Bruno", "clpid": "Crosignani-B" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Pickar", "given_name": "Kenneth A.", "clpid": "Pickar-K-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical microresonators have historically been perceived as structures that could efficiently confine optical energies. This is due to their exceedingly low losses at optical frequencies. This thesis has, for the first time, explored these structures in a starkly different frequency range. Optical microcavities like any other structure have mechanical eigenmodes or resonant modes of vibration with quality-factors representing the efficiency of energy storage at mechanical frequencies. It is shown here that micron size of these structures results in vibrations at radio frequencies (~1-100 MH), about seven orders of magnitude apart from the optical frequencies (~100 THz). Mechanical quality factors in excess of 5,000 are measured for toroidal microcavities revealing a heretofore unknown potential of these structures in storing energy at frequencies remarkably distant from their optical resonant modes. \r\n\r\nThis thesis describes how radiation-pressure or the force due to impact of photons could result in exceptionally strong couplings between the mechanical and optical resonators collocated within the same device. The discovered optomechanical coupling present in toroid microcavities is shown to reach such a high level that regenerative mechanical oscillations of the cavity structure are initiated with only micro-Watts of optical power. This is the first demonstration of radiation-pressure-induced mechanical oscillations in any type of optomechanical system. Embodied within a microscale, chip-based device, this mechanism can benefit both research into macroscale quantum mechanical phenomena and improve the understanding of the mechanism within the context of Laser interferometer gravitational-wave observatory (LIGO). It also suggests that new technologies are possible that will leverage the phenomenon within photonics.\r\n\r\nDifferent physical functionalities are also realized in this thesis by a combination of ultra-high-Q microtoroids and extremely low-loss tapered optical fibers for efficient delivery of optical power to these structures. Using these tools an almost ideal optical band-pass filter is designed with efficiencies solely limited by intrinsic losses of the optical resonator. These intrinsic loss mechanisms are experimentally studied and differentiated by a powerful technique based on thermal nonlinearities of the microcavity material. By taking advantage of slow response times of thermal effects, an innovative pump and probe technique is also developed to unveil and measure the Kerr nonlinearity in microcavities, for the first time, at room temperature.", "doi": "10.7907/CVT6-8J70", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:4499", "collection": "thesis", "collection_id": "4499", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11102006-175036", "primary_object_url": { "basename": "goodone.pdf", "content": "final", "filesize": 2348784, "license": "other", "mime_type": "application/pdf", "url": "/4499/2/goodone.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Theory, Fabrication and Applications of a Novel Archetype Semi-Ring Fabry-Perot (SRFP) Resonator and New Tiltmeters", "author": [ { "family_name": "Taghavi Larigani", "given_name": "Shervin", "orcid": "0000-0002-6599-7855", "clpid": "Taghavi-Larigani-Shervin" } ], "thesis_advisor": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "van Zyl", "given_name": "Jakob J.", "clpid": "van-Zyl-J-J" } ], "thesis_committee": [ { "family_name": "Hoffmann", "given_name": "Michael R.", "clpid": "Hoffmann-M-R" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "van Zyl", "given_name": "Jakob J.", "clpid": "van-Zyl-J-J" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The first instinct of any animal (including human) is surviving, which implies security. It impacts how we perceive the whole universe. The best way of satisfying this need, consists of being able to control situations in which we are immersed. One way of doing so, consists of predicting future events. That is why we perceive and model our environment based on cyclic and periodic events, going back to the earliest civilizations.
\r\n\r\nFew examples of such periodic events are:
\r\nSo modeling any sort of event happening in our environment by repetitive events allows us to enforce a secure feeling, since (periodic, cyclic) events have the advantage of being able to be foreseen, which provides the advantage of being well understood. Most of the devices fabricated by human beings are inspired by the perception of its environment, and somehow in most cases we just copy nature. Few examples are:
\r\nThat is why basic tools of many applied and engineering sciences are resonators, which are engineered devices that generate or sustain periodic or cyclic events. One example of a resonator is a guitar. The string can just take a certain finite number of shapes since it is bounded on its two extremes. Any excitation of the string can be decomposed as the excitation of each one of these shapes, which would repeat itself after one round trip. These shapes are called the resonant mode of the string. Each note (the music coming out of it) of the guitar corresponds to one of its resonant modes. The same way that we use a basis to describe a vector (for example x and y in the case of two dimensional vector), we can use the resonant modes as a basis to describe any intensity within the resonator. Therefore in the case of the guitar, any vibration of the string can be decomposed on a set of vibrations of each resonator mode, where the intensity of vibration of each mode is independent of the others. What differentiates any vibration of the string from another is the intensity with which this vibration couple, to each resonant mode. The same way that the guitar is a mechanical resonator, we can think of an electromagnetic resonator. The same way an electromagnetic resonator has different resonant modes, and each intensity couple to the resonator can be decomposed on a set of intensity of each resonant mode. Another example is at the atomic scales, where the atoms within a molecule have specific repetitive vibration and rotation patterns, which are called the resonant modes.
\r\n\r\nThe overall concept of a resonator is the same whether it is mechanical or electromagnetic one. The basic concept of a resonator is based upon a feedback, which guarantees the repetition of an event. At the root there are no more than two ways of obtaining such feedback.
\r\n\r\n1. The first idea consists of forcing the feedback. Due to this feed back the same event would happen at the same time if it is a temporal event or at the same location if it is a spatial event.
\r\n\r\nBy confining the event within a (temporal or spatial) barrier, and by being sure that the event would bounce back at that barrier, we would have created such a feedback. Such a specific barrier is often called a reflector. In the case of a mechanical resonator, such a reflector could be a wall. As an example, when someone talks within a confined structure, their voice gets echoed or resonates and in some cases the voice generated by the speaker would get back to him. This is a resonant phenomenon. Another example is if someone who is confined in a medium separated by two walls throws a ball to one of the walls. In a specific case, where the trajectory of the ball repeats itself, we talk about resonance. The same structure is also used in an electromagnetic resonator where the two reflectors are now electromagnetic reflectors. In the case of optics, the reflectors would be mirrors. In that case, the feedback would be obtained by confining an optical medium (a waveguide) within two optical reflectors (mirrors). Such a structure is the most basic archetype resonator in optics and was invented 100 years ago, and was named after its inventors Fabry-Perot. Fundamentally, this structure is very similar to the mechanical resonator obtained with the help of two walls.
\r\n\r\n2. Another way of thinking of such a feedback is by assuring that either the temporal or spatial path used by the events would be repeated. This can be obtained if the path shape is closed. An example of such structure is a circular shape.
\r\n\r\nIn this thesis, we present a completely novel resonator that in addition to having both the advantages of the first and the second types of resonators, has its own specific features. We have called this resonator a Semi-Ring Fabry-Perot (SRFP) resonator. In order to better understand this resonator we will focus ourselves in the field of optics, which emphasizes the best on the wave particularity of resonators. As we will see almost all optical resonators could be modeled as combinations of Fabry-Perot and ring resonators. These devices are the most important letter of the alphabet of the optics, where any device behaves like a word obtained with the combinations of the letters composing the alphabet, similar to introducing a new letter to the alphabet. Thus, we can with the use of this new letter create new words, which are new devices and could be useful. The benefit of the novel resonator that we introduce is beyond the scope of this thesis, where mostly optical applications of the resonator have been introduced.
\r\n\r\nAt the end of the thesis, we will introduce a novel way of measuring the incidence tilt of a field using a resonator.
\r\n", "doi": "10.7907/KC5S-1T19", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:3841", "collection": "thesis", "collection_id": "3841", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09302005-174955", "primary_object_url": { "basename": "thesisweb.pdf", "content": "final", "filesize": 3522270, "license": "other", "mime_type": "application/pdf", "url": "/3841/1/thesisweb.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Uncooled Carbon Microbolometer Imager", "author": [ { "family_name": "Liger", "given_name": "Matthieu", "clpid": "Liger-Matthieu" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Meng", "given_name": "Ellis", "clpid": "Meng E-F-C" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The discovery of infrared radiation two centuries ago and the theory of blackbody radiation one century later have given birth to the field of thermal imaging. Since then, researchers have devised numerous ways to detect infrared radiation. From World War II to the 1980s, semiconductor-based cooled photon detector arrays have reigned over the field of thermal imaging. Albeit limited to expensive, bulky systems used for military applications due to their cooling requirement they have been . The emergence of micromachining techniques in the 1980s however, have allowed for the development of uncooled, thermal detector arrays. Uncooled systems are expected to find more and more applications, especially in the civilian world.
\r\n\r\nHere we present a novel and simple way to fabricate uncooled infrared detectors suitable for integration into large-area arrays. The design is based on carbon obtained by means of polymer pyrolysis. We demonstrate how some electrical and thermal properties can be adjusted by process parameters, and then present the first micromachined carbon uncooled bolometer made of two-layers of self-supporting pyrolyzed-parylene carbon having different process-tuned properties.
\r\n\r\nFinally, based on this unique design and fabrication process, we develop a carbon bolometer array and demonstrate the thermal imaging capability by taking thermal images. Measurements show that the sensitivity to target temperature can be as low as 31mK and 44mK for 100us and 12us electrical signal integration time, respectively. This matches the current state of the art which is very promising considering the fact that this is the first time pyrolytic carbon has been used to fabricate a microbolometer array.
\r\n", "doi": "10.7907/R7HB-GF96", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:1594", "collection": "thesis", "collection_id": "1594", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05032006-154541", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 3011002, "license": "other", "mime_type": "application/pdf", "url": "/1594/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Classical and Quantum Nonlinear Optical Information Processing", "author": [ { "family_name": "Tsang", "given_name": "Mankei", "orcid": "0000-0001-7173-1239", "clpid": "Tsang-Mankei" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Hong", "given_name": "John Hyunchul", "clpid": "Hong-J-H" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is a theoretical investigation of the classical and quantum information processing enabled by the advent of modern ultrafast nonlinear optics.
\r\n\r\nChapter 2 and 3 study the propagation of ultrashort optical pulses in optical fibers, and propose two methods of compensating the linear and nonlinear distortions experienced by the pulses, namely, reverse propagation and spectral phase conjugation. Chapter 4 and 5 suggest different schemes that implement spectral phase conjugation.
\r\n\r\nChapter 6 and 7 establish the connection between classical spectral phase conjugation and quantum coincident frequency entanglement. Chapter 6 shows how a spectral phase conjugator can create coincident frequency entangled photon pairs, and Chapter 7 in turn demonstrates how a coincident frequency entanglement generator can perform spectral phase conjugation.
\r\n\r\nThe next three chapters, 8, 9, and 10, focus on quantum spatiotemporal information processing. Chapter 8 studies the temporal properties of entangled photon pair propagation and proposes the concept of quantum temporal imaging. Chapter 9 investigates how optical solitons can be used to perform quantum timing jitter reduction and temporal entanglement, while Chapter 10 applies the same idea to the spatial domain for quantum spatial information processing tasks, such as spatial beam displacement uncertainty reduction and quantum lithography.
\r\n\r\nThe final two chapters return to a couple of miscellaneous problems in classical optics. Chapter 11 shows how a pair of dielectric slabs can amplify the near field of an optical image. Chapter 12 explores the similarities between nonlinear optics and fluid dynamics, and speculates on the possibility of using nonlinear optics experiments to simulate fluid dynamics problems.
", "doi": "10.7907/BG6Y-VX33", "publication_date": "2006", "thesis_type": "phd", "thesis_year": "2006" }, { "id": "thesis:2423", "collection": "thesis", "collection_id": "2423", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06032005-115306", "primary_object_url": { "basename": "Yang_l_2005.pdf", "content": "final", "filesize": 10395220, "license": "other", "mime_type": "application/pdf", "url": "/2423/3/Yang_l_2005.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Fabrication and Characterization of Microlasers by the Sol-Gel Method", "author": [ { "family_name": "Yang", "given_name": "Lan", "orcid": "0000-0002-9052-0450", "clpid": "Yang-Lan" } ], "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": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The present study explores the application of new materials systems for low threshold microlasers, and characterization of the microcavities. The sol-gel method is used for gain functionalization of high-Q microcavities. A detailed procedure for preparation of the sol-gel films by the spin-on or dip-coating method is presented. The effect of different process conditions on the properties and microstructure of the thin films is investigated through Fourier Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), and etching rate test.
\r\n\r\nSurface gain functionalization of microsphere cavities is fabricated by coating the microsphere with a thin layer of Er\u00b3\u207a-doped sol-gel films. The optical gain is due to the population inversion of rare earth ions in the sol-gel films. A fiber taper is used to both couple the pump power into and extract the laser power out of the microsphere laser. The laser dynamics change between continuous-wave and pulsating operation by varying the doping concentration and the thickness of the sol-gel films outside the microsphere.
\r\n\r\nSurface functionalization is also achieved on the microtoroid on a single silicon chip, which can be fabricated in parallel using wafer-scale processing and has characteristics that are more easily controlled than microsphere. The microtoroid can be selectively coated only at the periphery by making use of the variation of etching rate (in buffered HF) of sol-gel films with different degrees of densification. The laser performance of the gain functionalized microtoroids is investigated. Highly confined whispering gallery modes make possible single-mode microlasers. This work also shows that the high Q microtoroid laser has a linewidth much lower than 300 kHz.
\r\n\r\nThe thesis explores fabrication of high Q microcavities directly from the sol-gel silica films deposited on a single silicon wafer. Quality factor as high as 2.5 x 10\u2077 at 1561 nm is obtained in toroidal microcavities formed of silica sol-gel, which allows Raman lasing at absorbed pump power below 1 mW. Additionally, Er\u00b3\u207a-doped microlasers are fabricated from Er\u00b3\u207a-doped sol-gel layers with control of the laser dynamics possible by varying the erbium concentration of the starting sol-gel material. Continuous lasing with a record threshold of 660 nW for erbium-doped microlaser on a silicon wafer is also obtained.
\r\n\r\nAnalytic formulas are derived to predict the laser performance, such as the laser output power, the threshold power, and the differential quantum efficiency, under different loading condition, i.e. the air gap between the fiber-taper coupler and the cavities. The effect of Er3+ concentration on the minimum threshold is also investigated. In addition, we present a theoretical model in which we include paired ions as the saturable absorber. It shows that self-pulsing operation can be expected with paired-ions-induced quenching in the system. The pulsation frequency increases linearly with the square root of the pumping level, which is consistent with the experimental observation.
", "doi": "10.7907/HHQ8-VC25", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:1621", "collection": "thesis", "collection_id": "1621", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05052005-131822", "primary_object_url": { "basename": "ThesisTeTe.pdf", "content": "final", "filesize": 2013868, "license": "other", "mime_type": "application/pdf", "url": "/1621/1/ThesisTeTe.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Operation of Holographic Elements with Broadband Light Sources", "author": [ { "family_name": "Hsieh", "given_name": "Hung-Te", "clpid": "Hsieh-Hung-Te" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Hong", "given_name": "John Hyunchul", "clpid": "Hong-J-H" }, { "family_name": "Buse", "given_name": "Karsten", "clpid": "Buse-K" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents the theoretical and experimental investigation of volume holography operated with broadband/polychromatic light sources, i.e., in both continuous-wave (linear) and femtosecond-pulse (nonlinear) regimes.
\r\n\r\nThe first chapter reviews the concept of volume holography and provides a tacit introduction to some basic properties of volume holograms and compares the operation of holograms in the spatial and temporal domains, preparing the readers for later chapters.
\r\n\r\nThe second chapter introduces a powerful theoretical tool for the analysis of volume holograms in the reflection geometry: the matrix formulation, laying the foundation for the application of holographic gratings utilized as WDM filters.
\r\n\r\nThe third chapter takes into consideration the effects of the practically inevitable finite beam-widths. By means of Fourier decomposition, the deviation of the filtering properties of volume holographic gratings from the ideal plane-wave case can be satisfactorily explained and predicted. Experiments and simulations are performed and compared to confirm the validity of the theory.
\r\n\r\nVolume holographic gratings in the reflection geometry serve as excellent WDM filters for telecommunication purposes thanks to their low cross-talk and readily engineered filtering properties. The theoretical design and experimental realization of athermal holographic filters are presented in the fourth chapter. By incorporating a passive, thermally actuated MEMS mirror, the temperature dependence of the Bragg wavelength of a holographic filter can be compensated.
\r\n\r\nThe analysis of holographic gratings in the 90 degree geometry requires a two dimensional theory. The relevant boundary conditions give rise to some peculiar behaviors in this configuration. Theory, simulations and some experimental results of the 90-degree holography are presented in chapter five.
\r\n\r\nThe sixth chapter delves into the subject of instantaneous Kerr index grating established by two intense, interfering femtosecond (pump) pulses at 388 nm owing to the omnipresent third-order nonlinearity. The coupled-mode equations describing the incident and diffracted (probe) pulses at 776 nm are written down; the solution is experimentally corroborated. It is further demonstrated that the temporal resolution in such a holographic pump-probe configuration does not degrade appreciably as the angular separation between pump pulses increases.
\r\n\r\nChapter seven investigates the nonlinear absorption processes in lithium niobate crystals with femtosecond pulses. The model of two-photon absorption well explains and anticipates the transmission coefficients of single pulses over a wide range of intensity. Collinear pump-probe transmission experiments are then carried out to look into the nonlinear absorption suffered by the probe pulse at 776 nm owing to the pump pulse at 388 nm; the dependence of the probe pulse transmission coefficient on the time delay between pump and probe pulses is characterized by a dip and a long-lasting plateau, which are attributed, respectively, to direct two-photon transitions involving pump and probe photons and the existence of free carriers.
\r\n\r\nBuilding on the experimental experience and theoretical understanding of the previous two chapters, the results of holographic pump-probe experiments in lithium niobate crystals are presented in the final chapter. The behavior is much more complicated because it encompasses all phenomena explored in the two preceding chapters, i.e., both the real and imaginary parts of the third-order susceptibility come into play in the instantaneous material response; furthermore, another mixed grating due to excited charge carriers exists long after the pump pulses pass through. Valuable information on the grating formation process is obtained thanks to the sub-picosecond temporal resolution of such configurations.
", "doi": "10.7907/9R5R-JT19", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:1717", "collection": "thesis", "collection_id": "1717", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05102005-112605", "primary_object_url": { "basename": "GTPaloczi_PhD_Thesis.pdf", "content": "final", "filesize": 7131872, "license": "other", "mime_type": "application/pdf", "url": "/1717/1/GTPaloczi_PhD_Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Polymer Integrated Optics: Device Architectures and Fabrication Methods", "author": [ { "family_name": "Paloczi", "given_name": "George T.", "clpid": "Paloczi-George-T" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Bockrath", "given_name": "Marc William", "clpid": "Bockrath-M-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Polymer materials are becoming increasingly important for integrated photonic circuits in optical communications networks. The optical and mechanical properties of polymers for integrated optics are explored in this thesis and it is shown that the manipulation of these properties leads to developments that in other optical materials could not be achieved as quickly or as easily, or not achieved at all.
\r\n\r\nSo that the benefits of a large range of operating wavelengths due to low material dispersion in polymers, are not lost to the wavelength dependence of optical couplers, we design wavelength-invariant couplers using a geometrical representation of coupled mode theory. Simulations of the resulting couplers confirm a virtually constant response over a large range of input wavelengths.
\r\n\r\nThe direct-write ability of electron beam sensitive polymers enables rapid fabrication of high-precision optical devices. Microring resonator optical filters and a compact microring-based inline reflector are fabricated by this method and characterized. Chaining multiple rings together results in the coupled resonator optical waveguide (CROW). A CROW-Mach-Zehnder interferometer is fabricated and the measured response corresponds well with the predictions based on the matrix theory.
\r\n\r\nPolymer materials can be patterned by a variety of methods not possible with traditional optical materials. Soft-stamp replica molding presents a means to further reduce the costs of implementing polymer materials. Demonstrating the potential of the method, microring resonators are fabricated, with excellent agreement between the responses of the original and the replica. To further demonstrate the effectiveness of the process, it is applied in the fabrication of Mach-Zehnder modulators. The modulators exhibit excellent properties, with single-arm modulation voltages of 8 V and extinction ratios better than 19 dB. Successive repetition of the molding process allows for multilayer polymer optical devices. Finally, the flexible properties of polymers are exploited for pliable, all-polymer freestanding optical circuits.
", "doi": "10.7907/W41G-2374", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2100", "collection": "thesis", "collection_id": "2100", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05262005-174627", "primary_object_url": { "basename": "01_Thesis_Centurion.pdf", "content": "final", "filesize": 4384306, "license": "other", "mime_type": "application/pdf", "url": "/2100/1/01_Thesis_Centurion.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Study of the Nonlinear Propagation of Femtosecond Laser Pulses", "author": [ { "family_name": "Centurion Mac Lean", "given_name": "Martin", "orcid": "0000-0002-5662-2293", "clpid": "Centurion-Mac-Lean-Martin" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Cross", "given_name": "Michael Clifford", "clpid": "Cross-M-C" } ], "local_group": [ { "literal": "div_pma" } ], "abstract": "This work presents a comprehensive study of the propagation of femtosecond pulses and the formation and evolution of spatial solitons. The first half (Chapters 2-3) is devoted to the implementation of a novel ultrafast holographic system to capture the nonlinear propagation of laser pulses with femtosecond resolution. Femtosecond pulses are used to record holograms of the ultrafast changes in the material properties. Amplitude and phase changes of the laser beam inside the medium are reconstructed numerically. The strength of the nonlinear material response and the density of free electrons can be recovered from the phase information in the hologram. A single hologram can be captured with fine spatial resolution, or a time-sequence of holograms can be captured in a single shot with reduced spatial resolution. We have observed dramatic differences in the light propagation depending on the material properties.
\r\n\r\nThe second part of the thesis (Chapters 4-5) covers the formation and evolution of spatial solitons in a Kerr medium. We have measured the evolution of the beam profile as a function of pulse energy and propagation length. The optical beam breaks up into a pattern of connected lines (constellation) and self-focused spots (solitons). The solitons self-focus to a minimum diameter and release their excess energy through conical emission, which in turn overlaps with the background constellation and seeds the formation of new solitons. The solitons also show a collective self-organizing behavior caused by their mutual interactions. The evolution of 1-D arrays of solitons was captured using Femtosecond Time-resolved Optical Polarigraphy, a technique that measures the transient birefringence induced by the pulses in the medium. When the array was generated in an unstable configuration, the solitons re-arranged themselves into an array with a (larger) more stable period. A transition to a chaotic state is observed when the input power is increased above a threshold level. A time-averaged pulse propagation equation was used to numerically solve for evolution of the beam. There was good agreement between the experimental results and the computer simulation.
", "doi": "10.7907/AZNE-B514", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2143", "collection": "thesis", "collection_id": "2143", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05272005-071800", "primary_object_url": { "basename": "Thesis-DornED-2005.pdf", "content": "final", "filesize": 5530781, "license": "other", "mime_type": "application/pdf", "url": "/2143/15/Thesis-DornED-2005.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Universal Biosignatures for the Detection of Life", "author": [ { "family_name": "Dorn", "given_name": "Evan David", "clpid": "Dorn-Evan-David" } ], "thesis_advisor": [ { "family_name": "Adami", "given_name": "Christoph Carl", "orcid": "0000-0002-2915-9504", "clpid": "Adami-C-C" }, { "family_name": "Nealson", "given_name": "Kenneth H.", "clpid": "Nealson-K-H" } ], "thesis_committee": [ { "family_name": "Adami", "given_name": "Christoph Carl", "orcid": "0000-0002-2915-9504", "clpid": "Adami-C-C" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Kirschvink", "given_name": "Joseph L.", "orcid": "0000-0001-9486-6689", "clpid": "Kirschvink-J-L" }, { "family_name": "Nealson", "given_name": "Kenneth H.", "orcid": "0000-0001-5189-3732", "clpid": "Nealson-K-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "My goal is to identify processes of life that leave measurable effects on an organism's environment, but which are not tied to any particular biochemistry, in order to build a conceptual framework for the search for extraterrestrial life. To this end, I test a pair of phenomena that appear in both terrestrial (biochemical) life and in digital life. Because these two life forms are different and unrelated, any phenomenon measurable in both is suggested to be universal.
\r\n\r\nThe Monomer Abundance Distribution Biosignature (MADB) is any measurement of the relative concentrations of related chemical compounds that cannot be explained by abiotic processes. I observe that living systems synthesize specific chemical compounds at rates that maximize their fitness. As a result, life-bearing environmental samples exhibit compounds in abundance ratios that are clearly not the result of abiotic synthesis because those ratios belie the formation kinetics and thermodynamics that would constrain abiotic synthesis. Often, biotic samples contain high concentrations of specific large, complex molecules that are never seen in abiotic synthesis and cannot be explained unless highly specific catalysts (i.e., enzymes) are present, and energy is expended to drive thermodynamically unfavorable reactions. I catalog this effect as it appears in terrestrial biochemical systems, including amino acids and carboxylic acids, and demonstrate the universality of selection's action on the monomeric composition of life forms by studying analogous examples in digital life. I suggest how this phenomenon provides a route to the detection of even unusual or unforeseen biochemistries, and give examples of detection methods using pattern-recognition techniques that may allow us to empower an autonomous system with the general ability to detect life forms.
\r\n\r\nThe Layered Trophic Residue Biosignature (LTRB) is any observation of stratification in solute chemistry that indicates metabolic activity by a sequence of diverse communities. When multiple chemical resources are available, natural selection drives adaptive radiation and the formation of specialist phenotypes. Competition ensures that specialists consume resources in decreasing order of energetic potential when resources diffuse through a medium near a boundary. The result is strata of chemicals appearing in order of redox potential, which is best explained by the presence of life.
\r\n", "doi": "10.7907/08B9-8Q96", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2146", "collection": "thesis", "collection_id": "2146", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05272005-113247", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 8099301, "license": "other", "mime_type": "application/pdf", "url": "/2146/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Ultra-High-Q Planar Microcavities and Applications", "author": [ { "family_name": "Armani", "given_name": "Deniz Karapetian", "clpid": "Armani-Deniz-Karapetian" } ], "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": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Ultra-high-Q (UHQ) silica microspheres have found research applications in diverse fields ranging from telecommunications to nonlinear optics to biological and chemical sensing. However, despite having quality factors greater than 108, the silica microsphere has not moved to an industrial setting because of several major drawbacks. The most hindering is the manual fabrication technique used that makes tight process control difficult and integration with other optical or electrical components impossible. Despite the strong desire to fabricate an integrated UHQ microresonator on a planar substrate, the highest quality factor achieved for any micro-fabricated planar micro-cavity (at the time of my first publication) was over 4 orders of magnitude lower than for silica microspheres. In this thesis, a process for creating planar micro-cavities with Q factors in excess of 400 million on silicon wafers is demonstrated. The advantage of these planar ultra-high-Q (UHQ) microtoroid resonators is that they successfully overcome the previously mentioned drawbacks of silica microsphere resonators while maintaining nearly identical, if not better, performance characteristics. Additionally, due to the planar nature of these new devices, functionality has been integrated in-situ while maintaining UHQ for the first time, such as active resonant frequency tuning, coupling control, and low-threshold lasing.", "doi": "10.7907/EZHA-VY23", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:1994", "collection": "thesis", "collection_id": "1994", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05242005-094353", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 16069175, "license": "other", "mime_type": "application/pdf", "url": "/1994/1/thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Dispersion in Photonic Crystals", "author": [ { "family_name": "Witzens", "given_name": "Jeremy", "orcid": "0000-0002-2896-7243", "clpid": "Witzens-Jeremy" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Yablonovitch", "given_name": "Eli", "clpid": "Yablonovitch-E" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Investigations on the dispersive properties of photonic crystals, modified scattering in ring-resonators, monolithic integration of vertical-cavity surface-emitting lasers and advanced data processing techniques for the finite-difference time-domain method are presented.
\r\n\r\nPhotonic crystals are periodic mesoscopic arrays of scatterers that modify the propagation properties of electromagnetic waves in a similar way as \"natural\" crystals modify the properties of electrons in solid-state physics. In this thesis photonic crystals are implemented as planar photonic crystals, i.e., optically thin semiconductor films with periodic arrays of holes etched into them, with a hole-to-hole spacing of the order of the wavelength of light in the dielectric media. Photonic crystals can feature forbidden frequency ranges (the band-gaps) in which light cannot propagate. Even though most work on photonic crystals has focused on these band-gaps for application such as confinement and guiding of light, this thesis focuses on the allowed frequency regions (the photonic bands) and investigates how the propagation of light is modified by the crystal lattice. In particular the guiding of light in bulk photonic crystals in the absence of lattice defects (the self-collimation effect) and the angular steering of light in photonic crystals (the superprism effect) are investigated. The latter is used to design a planar lightwave circuit for frequency domain demultiplexion. Difficulties such as efficient insertion of light into the crystal are resolved and previously predicted limitations on the resolution are circumvented. The demultiplexer is also fabricated and characterized.
\r\n\r\nMonolithic integration of vertical-cavity surface-emitting lasers by means of resonantly enhanced grating couplers is investigated. The grating coupler is designed to bend light through a ninety-degree angle and is characterized with the finite-difference time-domain method. The vertical-cavity surface-emitting lasers are fabricated and characterized.
\r\n\r\nA purely theoretical section of the thesis investigates advanced data processing techniques for the finite-difference time-domain method. In particular it is shown that an inner product can be used to filter out specific photonic crystal modes or photonic crystal waveguide modes (Bloch-modes). However it is also shown that the numerical accuracy of this inner product severely worsens for Bloch modes with very low group velocities.
", "doi": "10.7907/NV9T-SC75", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2002", "collection": "thesis", "collection_id": "2002", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05242005-162056", "primary_object_url": { "basename": "savarese_thesis.pdf", "content": "final", "filesize": 6963221, "license": "other", "mime_type": "application/pdf", "url": "/2002/1/savarese_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Shape Reconstruction from Shadows and Reflections", "author": [ { "family_name": "Savarese", "given_name": "Silvio", "clpid": "Savarese-Silvio" } ], "thesis_advisor": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" } ], "thesis_committee": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Arvo", "given_name": "James R.", "clpid": "Arvo-J-R" }, { "family_name": "Bruck", "given_name": "Jehoshua", "clpid": "Bruck-J" }, { "family_name": "Shimojo", "given_name": "Shinsuke", "clpid": "Shimojo-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Measuring automatically the shape of physical objects in order to obtain corresponding digital models has become a useful, often indispensable, tool in design, engineering, art conservation, computer graphics, medicine and science. Machine vision has proven to be more appealing than competing technologies. Ideally, we would like to be able to acquire digital models of generic objects by simply walking around the scene, while filming with a handheld camcorder. Thus, one of the main challenges in modern machine vision is to develop algorithms that: i) are inexpensive, fast and accurate; ii) can handle objects with arbitrary appearance properties and shape; and iii) need little or no user intervention.
\r\n\r\nIn this thesis, we address both issues. In the first part, we present a novel 3D reconstruction technique which makes use of minimal and inexpensive equipment. We call this technique \"shadow carving\". We explore the information contained in the shadows that an object casts upon itself. An algorithm is provided that makes use of this information. The algorithm iteratively recovers an estimate of the object which i) approximates the object\u2019s shape more and more closely; and ii) is provably an upper bound to the object's shape. Shadow carving is the first technique to incorporate \"shadow\" information in a multi-view shape recovery framework. We have implemented our approach in a simple table-top system and validated our algorithm by recovering the shape of real objects.
\r\n\r\nIt is well known that vision-based 3D scanning systems handle specular or highly reflective surfaces only poorly. The cause of this deficiency is most likely not intrinsic, but rather due to our lack of understanding of the relevant cues. In the second part of this thesis, we focus on how to promote mirror reflections from \"noise\" to \"signal\". We first present a geometrical and algebraic characterization of how a patch of the scene is mapped into an image by a mirror surface of given shape. We then develop solutions to the inverse problem of deriving surface shape from mirror reflections in a single image. We validate our theoretical results with both numerical simulations and experiments with real surfaces.
\r\n\r\nA third goal of this thesis is advancing our understanding of human perception of shape from reflections. Although the idea of perception of shape from different visual cues (e.g., shading, texture, etc.) has been extensively discussed in the past, little is known to what extent highlights and specular reflections carry useful information for shape perception. We use psychophysics to study this capability. Our goal is to provide a benchmark, as well as inspire possible technical approaches, for our computational work. We find that surprisingly, humans are very poor at judging the shape of mirror surfaces when additional visual cues (i.e., contour, shading, stereo, texture) are not visible.
", "doi": "10.7907/FH0V-3M10", "publication_date": "2005", "thesis_type": "phd", "thesis_year": "2005" }, { "id": "thesis:2242", "collection": "thesis", "collection_id": "2242", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05292005-111904", "primary_object_url": { "basename": "W_Green_thesis_final.pdf", "content": "final", "filesize": 6389623, "license": "other", "mime_type": "application/pdf", "url": "/2242/1/W_Green_thesis_final.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "InGaAsP-InP Semiconductor Microcavity Geometries for Annular Bragg Reflection, Optical Switching, and Sensing", "author": [ { "family_name": "Green", "given_name": "William M. J.", "clpid": "Green-William-M-J" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "One of the key mandates of modern optoelectronic research is the development of compact photonic integrated circuits, capable of performing many diverse functions for the generation, manipulation, and detection of light, all on a single chip. A key practical requirement for such circuits is the development of optical devices for the localization and processing of light within extremely small dimensions. In recent years, planar microring and microdisk resonators, in which light is confined by total internal reflection, have emerged as versatile photonic elements for filling this role. The high quality factors and long photon storage times associated with the whispering-gallery modes supported by these microcavities result in several technologically useful characteristics, including narrow-band filter response, and large resonant enhancement of the circulating electric field. These properties have been exploited in numerous passive and active device applications, including optical add/drop multiplexers, all-optical switches, and tunable lasers.
\r\n\r\nThis thesis describes the study of several unique ring-based optical microcavity geometries based upon the indium gallium arsenide phosphide/indium phosphide alloy semiconductor material system, undertaken in an effort to explore new optoelectronic architectures for confining and manipulating light.
\r\n\r\nThe first portion of this work involves the analysis and demonstration of a new microcavity geometry, in which cylindrical Bragg reflection is used for radial optical confinement, as an alternative to total internal reflection. In this class of structures, collectively known as annular Bragg resonators, light can be guided within a ring or pillar defect layer surrounded by cylindrical Bragg mirrors. Several microcavities based upon this configuration are designed and fabricated using a thin InGaAsP quantum well membrane. Using pulsed optical excitation, the characteristics of these structures as low threshold vertically emitting lasers is explored.
\r\n\r\nSecond, a total internal reflection-based coupled waveguide-resonator geometry, having applications to low power optical switching and modulation, is analyzed. This geometry makes use of the hybrid integration of a Mach-Zehnder interferometer with a racetrack resonator. Switching takes place using the Mach-Zehnder to control the coupling parameters in the vicinity of the critical coupling condition. Characterization of the static and dynamic output response of a thermooptically actuated InGaAsP-InP hybrid switch device demonstrates good ON-OFF switching contrast, microsecond response time, and reduced switching power in comparison with a conventional Mach-Zehnder configuration.
\r\n\r\nFinally, this work concludes by examining both the annular Bragg resonator and hybrid switch geometries in application to chemical and biological sensing. Both microcavity devices are shown to possess unique characteristics making them ideal for sensitive monitoring of small changes in the refractive index of a chemical or biological analyte.
", "doi": "10.7907/GGH2-AQ53", "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:2487", "collection": "thesis", "collection_id": "2487", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06072004-085555", "type": "thesis", "title": "Nonlinear Optics in Ultra-High-Q Whispering-Gallery Optical Microcavities", "author": [ { "family_name": "Kippenberg", "given_name": "Tobias Jan August", "orcid": "0000-0002-3408-886X", "clpid": "Kippenberg-Tobias-Jan-August" } ], "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": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical microcavities confine light at resonant frequencies for extended periods of time and fundamentally alter the interaction of light with matter. They are the basis of numerous applied and fundamental studies, such as cavity QED, photonics and sensing. Of all resonant geometries, surface tension-induced microcavities, such as silica micro-spheres, exhibit the highest Q-factor to date of nearly 9 billion. Despite these high Q-factor and the intense interest in these structures, the nonlinear optical properties of silica micro-spheres have remained nearly entirely unexplored. In this thesis the nonlinear optical phenomena which can occur in ultra-high-Q microcavities are investigated. To efficiently excite the whispering-gallery modes, tapered optical fibers are used and the coupling to ultra-high-Q modes studied. It is found, that microcavities with ultra-high enter a regime where scattering of light into the degenerate pair of clockwise and counter-clockwise mode is the dominant scattering process. In this regime the coupling properties are significantly altered, but the cavities still retain their ability to achieve significant cavity build-up fields. This allowed exceeding the threshold for all common nonlinearities encountered in silica. In particular, stimulated Raman scattering is observed in taper fiber coupled silica micro-spheres at threshold levels typically in the micro-Watt range, which usually is considered the regime of linear optics. Cascaded Raman lasing is also observed in these structures. The tapered optical fiber in these experiments functions to both pump WGMs as well as to extract the nonlinear Raman fields. In addition, the tapered-fiber coupling junction is highly ideal, making it possible to strongly over-couple ultra-high-Q cavities with negligible junction loss. This feature allows for the observation of very high internal differential photon conversion efficiencies approaching unity. Whereas micro-spheres are both compact and efficient nonlinear oscillators, their fabrication properties lack the control and parallelism typical of micro-fabrication techniques. A synergistic approach of micro-fabrication and a laser assisted reflow process, allows to create toroidally silica microcavities on a chip. In this thesis it is demonstrated, that these cavities can exhibit ultra-high-Q whispering-gallery modes, allowing to achieve ultra-high-Q modes on a chip. This results is a nearly four-order of magnitude improvement with respect to other wafer-scale microcavities. In addition their azimuthal mode-spectrum is strongly reduced. Nonlinear oscillation in these cavities has also been studied, and stimulated Raman scattering observed, allowing to achieve the first Raman laser on a chip. The devices show improved performance compared to micro-spheres due to a strongly reduced azimuthal mode spectrum, which allowed to observe single mode emission. The enhanced geometric control of these cavities is also studied and found to profoundly alter the nonlinear optical processes the toroid microcavities. Reduction of toroidal cross section is observed to cause a transition from stimulated Raman to parametric oscillation regime. This allowed to observe Kerr nonlinearity induced parametric oscillation in a microcavity for the first time. The parametrically generated \"twin beams\" exhibit high conversion efficiency and show near unity signal-to-idler ratio.
\r\n", "doi": "10.7907/T5B6-9R14", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:2130", "collection": "thesis", "collection_id": "2130", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05272004-095431", "primary_object_url": { "basename": "thesis_yoshie.pdf", "content": "final", "filesize": 9239740, "license": "other", "mime_type": "application/pdf", "url": "/2130/1/thesis_yoshie.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Planar Photonic Crystal Nanocavities with Active Quantum Nanostructures", "author": [ { "family_name": "Yoshie", "given_name": "Tomoyuki", "clpid": "Yoshie-Tomoyuki" } ], "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": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Mabuchi", "given_name": "Hideo", "clpid": "Mabuchi-H" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Extreme photon localization is applicable to constructing building blocks in photonic systems and quantum information systems. A finding fact that photon localization in small space modifies the radiation process was reported in 1944 by Purcell, and advances in fabrication technology enable such structures to be constructed at optical frequencies. Many demands of building compact photonic systems and quantum information systems have enhanced activities in this field. The photonic crystal cavity has potential in providing a cavity that supports only the fundamental mode of (lambda/2n)^3 together with good confinement of light within a resonator. This thesis addresses experimental and theoretical aspects of building such photon localization blocks embedding active quantum nanostructures in a planar photonic crystal platform. Examples given in this thesis are (1) quantum dot photonic crystal nanolasers, (2) high-speed photonic crystal nanolasers, and (3) light-matter coupling in a single quantum dot photonic crystal cavity system.
\r\n\r\n(1) A combination of quantum dots and photonic crystal nanocavities provides chirpless high-speed nanolasers. Room temperature low-threshold lasing action was demonstrated from a coupled cavity design (0.7 - 1.2(lambda/n)^3) embedding InAs/GaAs self-assembled quantum dots. The nanolasers showed small (absorbed) pumping power threshold as sub-20 microW and high spontaneous coupling factors of 0.1. Single quantum dot lasing is likely to occur both by proper alignment of the single quantum dot relative to geometries of photonic crystals and by a narrow QD emission line in the high-Q localized mode.
\r\n\r\n(2) Enhancement of radiation process in a small cavity was used to demonstrate high frequency relaxation oscillation up to 130 GHz. Built-in quantum well saturable absorbers enable us to probe the relaxation oscillation of such small lasers.
\r\n\r\n(3) Onset of intermediate light-matter coupling was demonstrated in a single quantum dot photonic crystal cavity system. A tripling in Q/V (quality factor divided by mode volume) is found to enable photons to start a strong interaction with a single quantum dot.
", "doi": "10.7907/WD4W-XQ37", "publication_date": "2004", "thesis_type": "phd", "thesis_year": "2004" }, { "id": "thesis:2372", "collection": "thesis", "collection_id": "2372", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06022003-042444", "primary_object_url": { "basename": "thesis_loncar_whole.pdf", "content": "final", "filesize": 9392553, "license": "other", "mime_type": "application/pdf", "url": "/2372/1/thesis_loncar_whole.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Nanophotonic Devices Based on Planar Photonic Crystals", "author": [ { "family_name": "Lon\u010dar", "given_name": "Marko", "orcid": "0000-0002-5029-5017", "clpid": "Lon\u010dar-Marko" } ], "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": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Mabuchi", "given_name": "Hideo", "clpid": "Mabuchi-H" }, { "family_name": "Quake", "given_name": "Stephen R.", "clpid": "Quake-S-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Photonic Crystals, man-made periodic structures with a high refractive index contrast modulation, have recently become very interesting platform for the manipulation of light. The existence of a photonic bandgap, a frequency range in which propagation of light is prevented in all directions, makes photonic crystals very useful in applications where spatial localization of light is required. Ideally, by making a three-dimensional photonic crystal, propagation of light in all three dimensions can be controlled. Since fabrication of 3-D structures is still a difficult process, a more appealing approach is based on the use of lower dimensional photonic crystals. A concept that has recently attracted a lot of attention is a planar photonic crystal based on a dielectric membrane, suspended in the air, and perforated with a two-dimensional lattice of holes.
\r\n\r\nIn this thesis theoretical and experimental study of planar photonic crystal nanolasers, waveguides and super-dispersive elements is presented. Room temperature operation of low-threshold nanolaser is demonstrated, both in air and in different chemical solutions. For the first time, we have demonstrated that photonic crystal nanocavity lasers can be used to perform spectroscopic tests on ultra-small volumes of analyte. Our porous cavity design permits the introduction of analyte directly into the high optical field of the laser cavity, and therefore it is ideally suited for the investigation of interaction between light and matter on a nanoscale level. We showed that small changes in refractive index of the ambient surrounding the laser can be detected by observing the shifts in emission wavelengths of the laser. Our lasers can be integrated into large arrays to permit the analysis of many reagents at the same time. The nanolasers can also be integrated with photonic crystal waveguides to form the integrated systems of higher complexities. Theoretical and experimental investigation of various photonic crystal waveguide designs is discussed. Details of the fabrication procedure used to realize nanophotonic devices in silicon on insulator as well as InGaAsP materials are presented.
", "doi": "10.7907/SB3Y-8Z20", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:1107", "collection": "thesis", "collection_id": "1107", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03252003-104132", "primary_object_url": { "basename": "Thesis_Yunping_Yang.PDF", "content": "final", "filesize": 1048938, "license": "other", "mime_type": "application/pdf", "url": "/1107/2/Thesis_Yunping_Yang.PDF", "version": "v4.0.0" }, "type": "thesis", "title": "Holographic Recording and Dynamic Range Improvement in Lithium Niobate Crystals", "author": [ { "family_name": "Yang", "given_name": "Yunping", "clpid": "Yang-Yunping" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Adibi", "given_name": "Ali", "clpid": "Adibi-A" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Chao", "given_name": "Tien-hsin", "clpid": "Chao-Tien-hsin" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents the results of research centered on the topic of improvement of dynamic range and sensitivity in volume holographic recording using photorefractive lithium niobate crystals. In general, there are two approaches to improving the dynamic range. One is at system level, the other approach is at material level. The second chapter compares the system performances of two holographic recording geometries (the 90-degree and transmission geometries) using iron-doped lithium niobate. The comparison is based on dynamic range, sensitivity, scattering noise, inter-pixel noise, and storage capacity. The third chapter investigates dark decay mechanisms in lithium niobate crystals. Two mechanisms of the dark decay, proton compensation and electron tunneling with activation energies of 1.0 eV and 0.28 eV, respectively, are identified. In crystals with low doping levels, proton compensation dominates the dark decay and extrapolation of lifetimes by an Arrhenius law to room temperature is valid. The time constant of this type of dark decay is inversely proportional to the proton concentration. For crystals with high doping levels, electron tunneling dominates the dark decay. This type of dark decay also limits the highest practical doping level in LiNbO3 crystals. For crystals with medium doping levels, both proton compensation and electron tunneling contribute significantly to the dark decay, and the single Arrhenius law does not hold with a single activation energy. In the fourth chapter, holographic data storage experiments are performed using manganese-doped lithium niobate crystals. The idea to use manganese-doped lithium niobate crystals for holographic storage is the direct result of the understanding of dark decay mechanisms discussed in Chapter 3. The experimental results of dark decay, M/#, sensitivity, multiplexing, thermal fixing, and holographic scattering for LiNbO3 : 0.2 atomic% Mn and LiNbO3 : 0.5 wt% MnCO3 are presented. The experimental results show that manganese-doped lithium niobate crystals are well suited for holographic storage. In the final chapter attention is focused on photorefractive properties of manganese-doped lithium niobate crystals. Material parameters, such as the distribution coefficient, are determined. Absorption measurements are used to obtain some information about several charge transport parameters. The dynamic range (M/#) and sensitivity for crystals of different doping levels, different oxidation states, and for different light polarizations have been measured.\r\n", "doi": "10.7907/V631-NJ22", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:2294", "collection": "thesis", "collection_id": "2294", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05302003-145931", "primary_object_url": { "basename": "gl-phd-thesis-bwprint.pdf", "content": "final", "filesize": 1887976, "license": "other", "mime_type": "application/pdf", "url": "/2294/1/gl-phd-thesis-bwprint.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Apertureless Near-Field Optical Microscopy for Fluorescence Imaging", "author": [ { "family_name": "Lessard", "given_name": "Guillaume", "orcid": "0000-0003-4275-3556", "clpid": "Lessard-Guillaume" } ], "thesis_advisor": [ { "family_name": "Quake", "given_name": "Stephen R.", "clpid": "Quake-S-R" } ], "thesis_committee": [ { "family_name": "Quake", "given_name": "Stephen R.", "clpid": "Quake-S-R" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Collier", "given_name": "C. Patrick", "clpid": "Collier-C-P" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Bockrath", "given_name": "Marc William", "clpid": "Bockrath-M-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes the development of a new type of optical microscope, an apertureless near-field microscope for fluorescence imaging (FANSOM). We have demonstrated that it is possible to use the probe of an atomic force microscope (AFM) to create a detectable modulation of the fluorescence of a nanometer-scale fluorescent object, and that it is possible to use that modulation to produce images by raster-scanning. Our results show that such a microscope is capable of a lateral resolution better than 20 nm.
\r\n\r\nThe processes that cause this modulation act for very small probe-sample separations, smaller than 20 nm. We have demonstrated FANSOM contrast using two completely different effects, one being a fluorescence inhibition, the other being a fluorescence enhancement generated by electric field enhancement. We have obtained contrast ratios of 1.90:1 using the fluorescence inhibition effect, and 5:1 using the fluorescence enhancement effect.
\r\n\r\nFluorescence can be inhibited by the proximity of a metallic probe. We have mapped the vertical profile of this phenomenon, and have shown that its shape is dependent upon the method of illumination. With evanescent illumination, the closest range of the interaction can exhibit some fluorescence enhancement that partially cancels the fluorescence inhibition effect.
\r\n\r\nWhen a metallic or dielectric probe approaches a sample illuminated by an evanescent illumination field polarized parallel to the probe (i.e., vertically with respect to the surface), field enhancement occurs. A local fluorescence enhancement is detected as a result of the field enhancement. The range of this effect is less than 10 nm, located mostly under the AFM probe; the optical images acquired using this contrast mechanism exhibit a lateral resolution equal to or higher than the topographic resolution measured by AFM.
\r\n\r\nThe design of the data acquisition system allows us to obtain precise mappings of signal intensity to probe--sample separation, more precise than have previously been achieved in an apertureless near-field microscopy system. It has allowed us to obtain repeatable approach curves that differ clearly from one another when the type of illumination or probe is changed.
", "doi": "10.7907/Y704-ER28", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:1527", "collection": "thesis", "collection_id": "1527", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04282003-142947", "primary_object_url": { "basename": "MyThesis.pdf", "content": "final", "filesize": 7129710, "license": "other", "mime_type": "application/pdf", "url": "/1527/1/MyThesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Holographic Information Systems", "author": [ { "family_name": "Panotopoulos", "given_name": "Georgios", "clpid": "Panotopoulos-Georgios" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Buse", "given_name": "Karsten", "clpid": "Buse-K" }, { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The goal of this work is to investigate the use of holographic techniques for information processing and transmission systems. Until recently information has been processed and transmitted mainly electronically. With the advent of optical fiber communications the monopoly of electronics has receded in the telecommunications field, but the domain of information processing is still dominated by electronic processors.
\r\n\r\nThis thesis follows a top-down approach to the design of processors that integrate both electronic and optical components. It begins with the design considerations of a compact, rapidly reconfigurable opto-electronic processor, which possesses an optical bus in addition to the traditional electronic bus. The optical bus takes advantage of the massive parallelism that is afforded by optics and can be coupled to a holographic digital memory, allowing rapid reconfiguration of the device. The capability of rapid reconfiguration gives rise to a new computational paradigm, where the reprogramming of the device can become part of the computation. We suggest additional applications of this processor, namely as a smart reading head for large scale holographic disk memories. Finally we present novel algorithms that were developed specifically to take advantage of the additional capabilities of our processor.
\r\n\r\nThe next section is concerned with the wavelength and angular tuning of strong volume holograms, both in the reflection and 90-degree geometries. Since photons have no charge, we need to rely on their wave properties to manipulate them, both for long-range transmission, such as telecommunications, and short-range transmission, such as on chip interconnects. In this section we investigate how volume holograms can be used to selectively redirect information bearing light beams.
\r\n\r\nThe final part of this thesis is concerned with material issues. Holographic recording of strong volume gratings is one of the most commonly used approaches, and photorefractive materials have a strong bearing on the overall performance of the final system. Two properties of iron doped lithium niobate are investigated, namely the dependence of absorption on temperature and the quadratic electro-optic coefficient. The former is crucial for the commonly used technique of thermal fixing, and the latter can become significant should we choose to use applied continuous fields to tune our gratings.
", "doi": "10.7907/P6B7-VR22", "publication_date": "2003", "thesis_type": "phd", "thesis_year": "2003" }, { "id": "thesis:6118", "collection": "thesis", "collection_id": "6118", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10072010-140426638", "primary_object_url": { "basename": "Feng_x_2002.pdf", "content": "final", "filesize": 8964952, "license": "other", "mime_type": "application/pdf", "url": "/6118/1/Feng_x_2002.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Methods for the Analysis of Visual Motion", "author": [ { "family_name": "Feng", "given_name": "Xiaolin", "clpid": "Feng-Xiaolin" } ], "thesis_advisor": [ { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" } ], "thesis_committee": [ { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "orcid": "0000-0002-3091-540X", "clpid": "Burdick-J-W" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Vision is a primary sense that allows human beings to interact with their environment and motion is one of the most important cues that vision can explore and utilize.\r\nIn this thesis, we present computational approaches to the problems of inferring three-dimensional motion information and perceiving two-dimensional human motions from a sequence of images captured by a camera.\r\nThe three-dimensional structure of world can be represented by distinguishable features, such as points. Assume all the features move under the same rigid motion in space, this motion can be recovered from the projections of the features in three views by solving a set of trilinear constraints. The trilinear constraints have been considered only as algebraic equations so that their satisfactory performance in motion estimation is not easy to understand. This thesis solves this puzzle by discovering a geometrical interpretation of trilinear constraints. It is showed that those algebraic equations correspond to depth errors appropriately weighted by a function of the relative reliability of the corresponding measurements. When the assumption is relaxed to allowing features to move under different rigid motions, this thesis proposes a three-dimensional motion based expectation-maximization algorithm combined with the modified separation matrix scheme to cluster the features undergoing the same motion into a group and estimate the motion for every group at the same time.\r\nThe problem of detecting and recognizing human motions arises from many applications in computer vision. This thesis describes an algorithm to detect human body from their motion patterns in a pair of frames which is based on learning an approximate probabilistic model of the positions and velocities of body joints. It then presents a scheme to recognize human actions in a sequence of frames assuming the human body is detected. This scheme enables us to simultaneously recognize both the action and the body poses in the observed sequence.\r\nAll our theoretical work is supported by experimental results.\r\n", "doi": "10.7907/SAVS-VJ68", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6262", "collection": "thesis", "collection_id": "6262", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03022011-094512699", "type": "thesis", "title": "Visual Sensors for Focal Plane Computation of Image Features", "author": [ { "family_name": "Pesavento", "given_name": "Alberto", "clpid": "Pesavento-Alberto" } ], "thesis_advisor": [ { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" } ], "thesis_committee": [ { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Diorio", "given_name": "Christopher J.", "clpid": "Diorio-Christopher-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Feature detection and tracking is a fundamental problem in computer vision research. By detecting and tracking features in an image sequence it is possible to recover\r\ninformation about both the motion of the viewer and the structure of the environment. The selection of features is a computationally intensive task. We derived two low-complexity algorithms that are suitable for integration in a CMOS sensor with focal-plane processing. We review the two algorithms and the circuits that implement them. We present results from accurate simulations and experimental results from the testing of these CMOS sensors.\r\n", "doi": "10.7907/BS04-5817", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "id": "thesis:6358", "collection": "thesis", "collection_id": "6358", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04272011-110550070", "primary_object_url": { "basename": "Liu_z_2002.pdf", "content": "final", "filesize": 55483438, "license": "other", "mime_type": "application/pdf", "url": "/6358/1/Liu_z_2002.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Optical Information Storage and Processing", "author": [ { "family_name": "Liu", "given_name": "Zhiwen", "clpid": "Liu-Zhiwen" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Quake", "given_name": "Stephen R.", "clpid": "Quake-S-R" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical information storage and optical information processing are the two themes of this thesis. Chapter two and three discuss the issue of storage while the final two chapters investigate the topic of optical computing.\r\n\r\nIn the second chapter, we demonstrate a holographic system which is able to record phenomena in nanosecond speed. Laser induced shock wave propagation is recorded by\r\nangularly multiplexing pulsed holograms. Five frames can be recorded with frame interval of 12ns and time resolution of 5.9ns. We also demonstrate a system which can record fast\r\nevents holographically on a CCD camera. Carrier multiplexing is used to store 3 frames in a single CCD frame with frame interval of 12ns. This technique can be extended to record femtosecond events.\r\n\r\nInformation storage in subwavelength structures is discussed in the third chapter. A 2D simulation tool using the FDTD algorithm is developed and applied to calculate the far field scattering from subwavelength trenches. The simulation agrees with the experimental data very well. Width, depth and angle multiplexing is investigated to encode information in subwavelength features. An eigenfunction approach is adopted to analyze how much\r\ninformation can be stored given the length of the feature. Finally we study the effect of nonlinear buffer layer.\r\n\r\nWe switch gear to holographic correlators in the fourth chapter. We study various properties of the defocused correlator which can control the shift invariance conveniently. An approximate expression of the shift selectivity is derived. We demonstrate a real time\r\ncorrelator with 480 templates. The cross talk of the correlators is also analyzed.\r\n\r\nFinally, in the fifth chapter we apply the optical correlator to fingerprint identification and study the performance of the correlation based algorithms. The windowed correlation can improve the rotation and distortion tolerance.", "doi": "10.7907/EVK8-H316", "publication_date": "2002", "thesis_type": "phd", "thesis_year": "2002" }, { "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:7366", "collection": "thesis", "collection_id": "7366", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01032013-152450777", "primary_object_url": { "basename": "billock_jg-2001.pdf", "content": "final", "filesize": 7511479, "license": "other", "mime_type": "application/pdf", "url": "/7366/1/billock_jg-2001.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Attentional Control of Complex Systems", "author": [ { "family_name": "Billock", "given_name": "Joseph Gregory", "clpid": "Billock-Joseph-Gregory" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Barbastathis", "given_name": "G.", "clpid": "Barbastathis-G" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis reports on work done in applying some of the concepts and architectures found in biological computation to computer algorithms. Biology has long inspired computer technology at the level of processing elements. This thesis explores the application of biologically inspired algorithms at a higher level-that of functional structures of the nervous system. The first chapter gives background on the attentional/awareness model of the brain, why it is important to biology and the advantages in real-time performance and in learning facilitation which we expect from applying it in computer algorithms.
\r\n\r\nThe second chapter examines the application of this model to a canonical computer science problem-the bin packing problem. Approaching this NP-complete problem when limited by computational resources and time constraints means that algorithms which throwaway large amounts of the information about the problem perform better than those which attempt to consider everything. The existence of an optimum in the size of a working memory needed to find the best solution under time pressure is shown. The transition between the regime of strict time constraints and more forgiving time constraints is quite sudden. Chapter 3 presents an analytical model for better understanding the performance of various bin packing algorithms.
\r\n\r\nChapter 4 examines the application of the attentional model to a real-time computer game testbed. This testbed is explained, and results are shown which illustrate that in a complex, unpredictable environment with tight time and resource constraints conditions, an algorithm which examines only that information which falls into a relatively small part of the playing area can win against player which addresses it all.
\r\n\r\nChapter 5 turns to an examination of the role of reduced informational representations upon learning. Solving of various logical-kinetic puzzles by a simulated segmented arm is done by a learning system. A logic supervisory subsystem utilizes attentional/awareness methods to train, and pass control of the different control levels of the articulate arm over to, the neural networks, adaptive resonance theory networks, and declarative computer memory which it trains. Finally, chapter 6 presents an overview and evaluation of the work.
", "doi": "10.7907/132r-jm11", "publication_date": "2001", "thesis_type": "phd", "thesis_year": "2001" }, { "id": "thesis:6098", "collection": "thesis", "collection_id": "6098", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10052010-135012445", "primary_object_url": { "basename": "Daniell_ce_2000.pdf", "content": "final", "filesize": 44278078, "license": "other", "mime_type": "application/pdf", "url": "/6098/1/Daniell_ce_2000.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Object Recognition in Compressed Imagery.", "author": [ { "family_name": "Daniell", "given_name": "Cynthia Evors", "clpid": "Daniell-Cynthia-Evors" } ], "thesis_advisor": [ { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" } ], "thesis_committee": [ { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "It is often necessary to search for objects in large databases of compressed imagery. In the past, object recognition and image compression have generally been treated as separate problems, resulting in inefficient suboptimal performance. Moreover, computational and storage issues make it fundamentally prohibitive to uncompress large images prior to object recognition. We provide two complementary solutions to the problem of object recognition in compressed imagery, each of which integrates subband and correlation filtering in a unique manner.
\r\n\r\nOne key benefit of correlation filters is that, as linear systems, they are highly compatible with the subband filtering process. This enables us to provide a seamless operation in which object recognition and data compression are viewed as continuations of the same process. The public MSTAR data set illustrates our results on a three class problem of 79 Synthetic Aperture Radar images at one foot resolution.
\r\n\r\nOur general framework, the Pattern Recognition Subband Coder (PRSC), provides simultaneous synthesis and recognition at full resolution in a computationally efficient architecture. Its parallelism enables a result 1.6 times faster, in the limit, than correlation on uncompressed imagery. Furthermore, by jointly optimizing the synthesis and recognition filters, the PRSC achieves 100% recognition accuracy on our compressed data set, improving performance over that produced from the original (uncompressed) data set, by 3.7%. We maintain this success for compression ratios up to 6:1.
\r\n\r\nAddressing the issue of reduced resolution recognition, our Subband Domain Correlation Filters operate directly on the subband coefficients at multiple resolution levels. For compression ratios of at least 20:1, we achieve recognition performance of at least 90%, 85%, and 75%, respectively, on two, four, and eight foot resolution data.
\r\n\r\nThus, through our solutions with compressed imagery, we outperform correlation results on the equivalent original imagery in terms of both speed and accuracy, as well as provide success at reduced resolutions of the data.
", "doi": "10.7907/6z3z-ar86", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:962", "collection": "thesis", "collection_id": "962", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03152006-094551", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 3498167, "license": "other", "mime_type": "application/pdf", "url": "/962/1/thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Visual input for pen-based computers", "author": [ { "family_name": "Munich", "given_name": "Mario Enrique", "orcid": "0000-0002-6665-7473", "clpid": "Munich-M-E" } ], "thesis_advisor": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" } ], "thesis_committee": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Arvo", "given_name": "James R.", "clpid": "Arvo-J-R" }, { "family_name": "Burl", "given_name": "Michael C.", "clpid": "Burl-M-C" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The development of computer technology has had a parallel evolution of the interface between humans and machines, giving rise to interface systems inspired by human communication. Vision has been demonstrated to be the sense of choice for face recognition, gesture recognition, lip reading, etc. This thesis presents the design and implementation of a camera-based, human-computer interface for acquisition of handwriting. The camera focuses on the sheet of paper and images the hand writing; computer analysis of the resulting sequence of images enables the trajectory of the pen to be tracked and the times when the pen is in contact with the paper to be detected. The recovered trajectory is shown to have sufficient spatio-temporal resolution and accuracy to enable handwritten character recognition.\r\n\r\nSignatures can be acquired with the camera-based interface with enough resolution to perform verification. This thesis describes the performance of a visual-acquisition signature verification system, emphasizing the importance of the parameterization of the signature to achieving good classification results. The generalization error of the verification algorithm is estimated using a technique that overcomes the small number of example signatures and forgeries provided by the subjects.\r\n\r\nThe problem of establishing correspondence and measuring the similarity of a pair of planar curves, in our case a pair of signatures, arises in many application in computer vision and pattern recognition. This thesis presents a new method for comparing planar curves and for performing matching at sub-sampling resolution. The analysis of the algorithm as well as its structural properties are described. The performance of the new technique is evaluated for the problem of signature verification and compared to the performance of the well-known Dynamic Programming Matching algorithm.", "doi": "10.7907/1VW0-ZG46", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:4722", "collection": "thesis", "collection_id": "4722", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12022005-103530", "primary_object_url": { "basename": "Itti_l_2000.pdf", "content": "final", "filesize": 30679584, "license": "other", "mime_type": "application/pdf", "url": "/4722/1/Itti_l_2000.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Models of Bottom- Up and Top-Down Visual Attention", "author": [ { "family_name": "Itti", "given_name": "Laurent", "orcid": "0000-0002-0168-2977", "clpid": "Itti-Laurent" } ], "thesis_advisor": [ { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" } ], "thesis_committee": [ { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Andersen", "given_name": "Richard A.", "orcid": "0000-0002-7947-0472", "clpid": "Andersen-R-A" }, { "family_name": "Shimojo", "given_name": "Shinsuke", "orcid": "0000-0002-1290-5232", "clpid": "Shimojo-S" } ], "local_group": [ { "literal": "Koch Laboratory (KLAB)" }, { "literal": "div_biol" } ], "abstract": "When we observe our visual environment, we do not perceive all its components as being equally interesting. Some objects automatically and effortlessly \"pop out\" from their surroundings, that is, they draw our visual attention, in a \"bottom up\" manner, towards them. In a first approximation, focal visual attention acts as a rapidly shiftable \"spotlight,\" which allows only the selected information to reach higher levels of processing and representation. Most models of the bottom-up control of attention are based on the concept of a saliency map, that is, an explicit two-dimensional map that encodes the conspicuity of objects in the visual environment. Competition among neurons in this map gives rise to a single winning location that corresponds to the next attended target. Inhibiting this location automatically allows the system to attend to the next most salient location. A first body of work in this thesis describes a detailed computer implementation of such a scheme, focusing on the problem of combining information across modalities, here orientation, intensity and color information, in a purely stimulus-driven manner. The model is applied to common psychophysical stimuli as well as to very demanding visual search tasks. Its successful performance is used to address the extent to which the primate visual system carries out visual search via one or more such saliency maps and how this can be tested.
\r\n\r\nWe next address the question of what happens once our attention is focused onto a restricted part of our visual field. There is mounting experimental evidence that attention is far more sophisticated than a simple feed-forward spatially-selective filtering process. Indeed, visual processing appears to be significantly different inside the attentional spotlight than outside. That is, in addition to its properties as a feed-forward information processing and transmission bottleneck, focal visual attention feeds back and locally modulates, in a \"top down\" manner, the visual processing and representation of selected objects. The second body of work presented in this thesis is concerned with a detailed computational model of basic pattern vision in humans and its modulation by top-down attention. We start by acquiring a complete dataset of five different simple psychophysical experiments, including discriminations of contrast, orientation and spatial frequency of simple pattern stimuli by human observers. This experimental dataset places strict constraints on our model of early pattern vision. The model, however, is eventually able to reproduce the entire dataset while assuming plausible neurobiological components. The model is further applied to existing psychophysical data which demonstrates how top-down attention alters performance in these simple psychophysical discrimination experiments. Our model is able to quantitatively account for all observations by assuming that attention strengthens the non-linear cortical interactions among visual neurons.
\r\n\r\nTogether, the two aspects of attention studied in this thesis lead us to consider the essential role of non-linear computations in visual processing. We suggest that visual processing, even at its earliest levels, is best characterized not by linear response functions and spatial convolutions, but rather by non-linearly interacting computational devices.
", "doi": "10.7907/MD7V-NE41", "publication_date": "2000", "thesis_type": "phd", "thesis_year": "2000" }, { "id": "thesis:3690", "collection": "thesis", "collection_id": "3690", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09222005-111015", "primary_object_url": { "basename": "Song_x_1999.pdf", "content": "final", "filesize": 4242947, "license": "other", "mime_type": "application/pdf", "url": "/3690/1/Song_x_1999.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Contextual pattern recognition with applications to biomedical image identification", "author": [ { "family_name": "Song", "given_name": "Xubo", "clpid": "Song-Xubo" } ], "thesis_advisor": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "thesis_committee": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Kasdan", "given_name": "Harvey L.", "clpid": "Kasdan-H-L" }, { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis studies two rather distinct topics: one is the incorporation of contextual information in pattern recognition, with applications to biomedical image identification; and the other is the theoretical modeling of learning and generalization in the regime of machine learning.\r\n\r\nIn Part I of the thesis, we propose techniques to incorporate contextual information into object classification. In the real world there are cases where the identity of an object is ambiguous due to the noise in the measurements based on which the classification should be made. It is helpful to reduce the ambiguity by utilizing extra information referred to as context, which in our case is the identities of the accompanying objects. We investigate the incorporation of both full and partial context. Their error probabilities, in terms of both set-by-set error and element-by-element error, are established and compared to context-free approach. The computational cost is studied in detail for full context, partial context and context-free cases. The techniques are applied to toy problems as well as real world problems such as white blood cell image classification and microscopic urinalysis. It is demonstrated that superior classification performance is achieved by using context. In our particular application, it reduces overall classification error, as well as false positive and false negative diagnosis rates.\r\n\r\nIn Part II of the thesis, we propose a novel theoretical framework, called the Bin Model, for learning and generalization. Using the Bin Model, a closed form is derived for generalization that estimates the out-of-sample performance in terms of the in-sample performance. We address the problems of overfitting, and characterize conditions under which it does not appear. The effect of noise on generalization is studied, and the generalization of the Bin Model framework from classification problems to regression problems is discussed.\r\n", "doi": "10.7907/F5YK-HM52", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:541", "collection": "thesis", "collection_id": "541", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02072008-115723", "primary_object_url": { "basename": "Bouguet_jy_1999.pdf", "content": "final", "filesize": 15501518, "license": "other", "mime_type": "application/pdf", "url": "/541/1/Bouguet_jy_1999.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Visual methods for three-dimensional modeling", "author": [ { "family_name": "Bouguet", "given_name": "Jean-Yves", "clpid": "Bouguet-J" } ], "thesis_advisor": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" } ], "thesis_committee": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" }, { "family_name": "Barr", "given_name": "Alan H.", "clpid": "Barr-A-H" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Antonsson", "given_name": "Erik K.", "clpid": "Antonsson-E-K" }, { "family_name": "Arvo", "given_name": "James R.", "clpid": "Arvo-J-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Most animals use vision as a primary sensor to interact with their environment. Navigation or manipulation of objects are among the tasks that can be better achieved while understanding the three-dimensional structure of the scene.\n\nIn this thesis, we present a variety of computational techniques for estimating 3D shape from 2D images, based on both passive and active technologies.\n\nThe first proposed method is purely passive. In this technique, a single camera is moved in an unconstrained manner around the scene to model as it acquires a sequence of images. The reconstruction process consists then of retrieving the trajectory of the camera, as well as the 3D structure of the scene using only the information contained in the images.\n\nThe second method is based on active lighting technology. In the philosophy of standard 3D scanning methods, a projector is used to project light patterns in the scene. The shape of the scene is then inferred from the way the patterns deform on the objects. The main novelty of our scheme compared to traditional methods is in the nature of the patterns, and the type of image processing associated to them. Instead of using standard binary patterns made out of black and white stripes, our scheme uses a sequence of grayscale patterns with a sinusoidal profile in brightness intensity. This choice allows us to establish correspondence (between camera image, and projector image) in a dense fashion, leading to depth computation at (almost) \nevery pixel in the image.\n\nThe last reconstruction method that we propose in this thesis is an alternative 3D scanning scheme that does not require any other device besides a camera. The main idea is to substitute the projector by a standard light source (such as a desk lamp), and use a pencil (or any other object with a straight edge) to cast planar shadows in the scene. The 3D geometry of the scene is then inferred from the way the shadow naturally deforms on the objects in the scene. Since this technology is largely inspired from structured lighting techniques, we call it 'weakly structured lighting.'\n", "doi": "10.7907/hc2c-sp47", "publication_date": "1999", "thesis_type": "phd", "thesis_year": "1999" }, { "id": "thesis:428", "collection": "thesis", "collection_id": "428", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02012005-154636", "primary_object_url": { "basename": "Chuang_ey_1998.pdf", "content": "final", "filesize": 10261557, "license": "other", "mime_type": "application/pdf", "url": "/428/1/Chuang_ey_1998.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Methods and architecture for rewritable holographic memories", "author": [ { "family_name": "Chuang", "given_name": "Ernest Y.", "clpid": "Chuang-E-Y" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "The focus of this thesis relates to issues of concern for rewritable holographic memories, primarily the volatility of recordings made in photorefractive crystals, which are the most likely class of materials to be used for such applications. Holograms written in such crystals tend to gradually decay under illumination, leading to the loss of information. We examine two candidate approaches for dealing with this problem of volatility: the dual wavelength method and the periodic copying technique. We also investigate various potential system architectures for dynamic holographic memories.\n\nIn Chapter 2 we analyze the dual-wavelength method, which makes use of different wavelengths for recording and readout to reduce the grating decay while retrieving data. Bragg-mismatch problems from the use of two wavelengths are minimized through recording in the image plane and using thin crystals. We combine peristrophic multiplexing with angle multiplexing to counter the poorer angular selectivity of thin crystals. We successfully store 1000 holograms in this manner and demonstrate a significantly reduced decay rate. However, we find that dark conductivity reduces the effectiveness of this method for nonvolatile readout, and constraints placed on the usable pixel sizes limit this method to moderate storage densities.\n\nIn Chapter 3 we examine the periodic copying technique, in which a stored set of holograms is intermittently refreshed to prevent the loss of any information. We show the necessity of using a fixed-time recording schedule with such systems and derive optimum exposure times for maximizing storage capacity. Our analysis includes both purely refreshed memories and memories with active erasure and rewrite capabilities.\n\nFrom our research in the preceding two chapters, we find periodic copying to be the more complementary of the two approaches, and in Chapter 4 we proceed to study possible memory system architectures that could incorporate the copying technique. We seek to do this while decreasing the system size and increasing the access speed over that of typical holographic systems that have been demonstrated thus far. We find that we can design a compact lensless memory by using the phase-conjugate readout method in combination with a smart-pixel array that combines the functions of a spatial,light modulator and detector array. Rapid random access speeds can be achieved by using laser arrays such as VCSELs (vertical-cavity surface-emitting lasers). We calculate the optimum storage density of this model to be 160bits/[square cm] of system volume.\n\nIn Chapter 5 we present experimental results from combining the periodic copying technique with conjugate-readout architectures and demonstrate the operation of a prototype version of the smart-pixel array described earlier. We show that the conjugate readout method yields reconstructed image fidelity at least as good as can be obtained by high-quality imaging systems. We also show the successful refreshment of 25 holograms for 100 cycles with no errors and no appreciable deterioration in image quality. Comparisons with the predictions from Chapter 3 indicate consistency between theory and experiment.\n\nFinally in Chapter 6 we summarize our results and discuss future work to continue this research.\n", "doi": "10.7907/7ATJ-GM53", "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:263", "collection": "thesis", "collection_id": "263", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01212009-150209", "primary_object_url": { "basename": "An_x_1998.pdf", "content": "final", "filesize": 28198921, "license": "other", "mime_type": "application/pdf", "url": "/263/1/An_x_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Long-term large-scale holographic storage in LiNbO33:Fe", "author": [ { "family_name": "An", "given_name": "Xin", "clpid": "An-Xin" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "The organization of this thesis very much coincides with the progress and \"evolution\" of my work here at Caltech. I came in at a time when our research activities entered a phase of full-scale realization of holographic storage after theoretical model building and proof-of-principle investigations were successfully carried out. More and more efforts have been dedicated to various experimental examination and demonstrations. Therefore, the major portion of this thesis details results from these efforts. Theoretical treatments are developed when necessary and only serve as the starting point and justification of further, serious experimentation.\r\n\r\nThe centerpiece of my work described in this thesis is a large-scale fast random-access holographic memory using LiNbO[subscript 3]Fe. It is not only our first attempt to incorporate many important disciplines and understandings of holographic memory design, engineering and experimentation to construct a real working prototype, but also a tool and test-bed for later characterization and investigation of other aspects in the application of holographic storage technology. This system is described in detail in Chapter 2 and 3 and has been used repeatedly and extensively through all of our works. Another two threads in the work presented here are the use of the M/# as a system metric to evaluate the dynamic range limitations, and of the Signal-to-Noise Ratio (SNR) and Bit-Error Rate (BER) to characterize the system error performance.\r\n\r\nIn Chapter 2, the design of a large-scale random-access holographic memory using LiNbO[subscript 3]Fe is discussed in detail. High, system dynamic-range-limited storage capacity is demonstrated by using angle, fractal and spatial multiplexing with a key custom-designed component\u2014the segmented mirror array. The SNR and BER obtained from the reconstructed information are comparable to those of conventional CD-ROMs.\r\n\r\nFast random access to the memory contents is materialized in a separate system using an acousto-optic deflector (AOD) as the addressing device and an electro-optic modulator (EOM) to compensate for the Doppler shift. Chapter 3 discusses the design issues and presents experimental demonstration of holographic storage using the system. The design and application of an optical phase-lock loop using the AOD and EOM for phase stabilization are also described at the end of this chapter.\r\n\r\nChapter 4 and 5 address two methods of thermal fixing to solve the volatility problem in holographic memories using photorefractive materials. First, \"Low-High-Low\" fixing is described in Chapter 4, along with the characterization of system error performance of non-volatile holographic storage using thermal fixing. A novel \"incremental fixing schedule\" is introduced to improve the system fixing efficiency. Experimental demonstration of a large-scale non-volatile memory with good error performance is also presented.\r\n\r\nChapter 5 shows theoretical treatment and experimental demonstration of high-temperature recording in LiNb0[subscript 3]Fe. Different charge transport mechanisms and their influence on the dynamics of holographic recording as well as the system dynamic range are discussed in detail. The two thermal fixing methods are examined and compared in terms of the M/#.\r\n\r\nIn Chapter 6, a very important holographic noise source, the inter-pixel grating noise, is evaluated theoretically based on a linear (small-signal) model, followed by experimental investigation of its influence on the system error performance of a large-scale memory. Random-phase modulation in the signal beam is discussed and demonstrated as an effective way to suppress this holographic noise.\r\n", "doi": "10.7907/41ay-1344", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:986", "collection": "thesis", "collection_id": "986", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03172008-142604", "primary_object_url": { "basename": "Barbastathis_g_1998.pdf", "content": "final", "filesize": 10693439, "license": "other", "mime_type": "application/pdf", "url": "/986/1/Barbastathis_g_1998.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Intelligent holographic databases", "author": [ { "family_name": "Barbastathis", "given_name": "George", "clpid": "Barbastathis-George" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Whitham", "given_name": "Gerald Beresford", "clpid": "Whitham-G-B" }, { "family_name": "Franklin", "given_name": "Joel N.", "clpid": "Franklin-J-N" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Andersen", "given_name": "Richard A.", "orcid": "0000-0002-7947-0472", "clpid": "Andersen-R-A" }, { "family_name": "Shimojo", "given_name": "Shinsuke", "orcid": "0000-0002-1290-5232", "clpid": "Shimojo-S" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "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\nMemory is a key component of intelligence. In the human brain, physical structure and functionality jointly provide diverse memory modalities at multiple time scales. How could we engineer artificial memories with similar faculties? In this thesis, we attack both hardware and algorithmic aspects of this problem.\r\n\r\nA good part is devoted to holographic memory architectures, because they meet high capacity and parallelism requirements. We develop and fully characterize shift multiplexing, a novel storage method that simplifies disk head design for holographic disks. We develop and optimize the design of compact refreshable holographic random access memories, showing several ways that 1 Tbit can be stored holographically in volume less than 1 [...], with surface density more than 20 times higher than conventional silicon DRAM integrated circuits. To address the issue of photorefractive volatility, we further develop the two-lambda (dual wavelength) method for shift multiplexing, and combine electrical fixing with angle multiplexing to demonstrate 1,000 multiplexed fixed holograms. Finally, we propose a noise model and an information theoretic metric to optimize the imaging system of a holographic memory, in terms of storage density and error rate.\r\n\r\nMotivated by the problem of interfacing sensors and memories to a complex system with limited computational resources, we construct a computer game of Desert Survival, built as a high-dimensional non-stationary virtual environment in a competitive setting. The efficacy of episodic learning, implemented as a reinforced Nearest Neighbor scheme, and the probability of winning against a control opponent improve significantly by concentrating the algorithmic effort to the virtual desert neighborhood that emerges as most significant at any time. The generalized computational model combines the autonomous neural network and von Neumann paradigms through a compact, dynamic central representation, which contains the most salient features of the sensory inputs, fused with relevant recollections, reminiscent of the hypothesized cognitive function of awareness. The Declarative Memory is searched both by content and address, suggesting a holographic implementation. The proposed computer architecture may lead to a novel paradigm that solves \"hard\" cognitive problems at low cost.\r\n", "doi": "10.7907/1R63-9H50", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:3689", "collection": "thesis", "collection_id": "3689", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09222005-110351", "primary_object_url": { "basename": "Sill_j_1998.pdf", "content": "final", "filesize": 3275897, "license": "other", "mime_type": "application/pdf", "url": "/3689/1/Sill_j_1998.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Monotonicity and connectedness in learning systems", "author": [ { "family_name": "Sill", "given_name": "Joseph", "clpid": "Sill-J" } ], "thesis_advisor": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "thesis_committee": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Bruck", "given_name": "Jehoshua", "clpid": "Bruck-J" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis studies two properties- monotonicity and connectedness- in the context of machine learning. The first part of the thesis examines the role of monotonicity constraints in machine learning from both practical and theoretical perspectives. Two techniques for enforcing monotonicity in machine learning models are proposed. The first method adds to the objective function a penalty term measuring the degree to which the model violates monotonicity. The penalty term can be interpreted as a Bayesian prior favoring functions which obey monotonicity. This method has the potential to enforce monotonicity only approximately, making it appropriate for situations where strict monotonicity may not hold. The second approach consists of a model which is monotonic by virtue of functional form. This model is shown to have universal approximation capabilities with respect to the class M of monotonic functions. A variety of theoretical results are also presented regarding M. The generalization behavior of this class is shown to depend heavily on the probability distribution over the input space. Although the VC dimension of M is [infinity], the VC entropy (i.e., the expected number of dichotomies) is modest for many distributions, allowing us to obtain bounds on the generalization error. Monte Carlo techniques for estimating the capacity and VC entropy of M are presented.\n\nThe second part of the thesis considers broader issues in learning theory. Generalization error bounds based on the VC dimension describe a function class by counting the number of dichotomies it induces. In this thesis, a more detailed characterization is presented which takes into account the diversity of a set of dichotomies in addition to its cardinality. Many function classes in common usage are shown to possess a property called connectedness. Models with this property induce dichotomy sets which are highly clustered and have little diversity. We derive an improvement to the VC bound which applies to function classes with the connectedness property.\n", "doi": "10.7907/GQWN-1H71", "publication_date": "1998", "thesis_type": "phd", "thesis_year": "1998" }, { "id": "thesis:177", "collection": "thesis", "collection_id": "177", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01142008-093315", "primary_object_url": { "basename": "Pu_a_1997.pdf", "content": "final", "filesize": 20036774, "license": "other", "mime_type": "application/pdf", "url": "/177/1/Pu_a_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Holographic 3-D disks and optical correlators using photopolymer materials", "author": [ { "family_name": "Pu", "given_name": "Allen", "clpid": "Pu-A" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\n\nThis thesis presents an experimentalist's approach to data storage and information processing using volume holography. In Chapter 1, a short introduction in volume holography and some commonly used recording materials are presented. Chapter 2 discusses in detail a specific recording material, the DuPont photopolymer. The recording behavior of the DuPont photopolymer was fully characterized by using a new multiplexing method called peristrophic multiplexing. From its recording behavior, we were able to derive an exposure schedule to multiplex equal strength holograms in the same volume. This method of determining the exposure schedule was put to the test by multiplexing 1,000 holograms in a piece of photopolymer that is only 100 microns thick.\n\nOne of the goals of this thesis is to demonstrate that information can be stored much more densely using holography. In Chapter 3, results from several different high density holographic data storage experiments are presented. In one experiment, a surface density of 100 bits/[...] was achieved. That is approximately two orders of magnitude higher than the compact discs we use today.\n\nHolography can also be used to process a vast amount of information very quickly through the parallel nature of optics. Chapter 4 shows how optical correlator systems, using a holographic database, can be trained to perform complex tasks. By programming the holographic database appropriately, we have used optical correlator systems to navigate an autonomous vehicle, to recognize/track a target, and to identify users through sequential fingerprint inputs.\n", "doi": "10.7907/qjzx-9z05", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:93", "collection": "thesis", "collection_id": "93", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01092008-094943", "primary_object_url": { "basename": "Burl_mc_1997.pdf", "content": "final", "filesize": 15718715, "license": "other", "mime_type": "application/pdf", "url": "/93/1/Burl_mc_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Recognition of visual object classes", "author": [ { "family_name": "Burl", "given_name": "Michael C.", "clpid": "Burl-M-C" } ], "thesis_advisor": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" } ], "thesis_committee": [ { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Franklin", "given_name": "Joel N.", "clpid": "Franklin-J-N" }, { "family_name": "Simon", "given_name": "Marvin K.", "clpid": "Simon-M-K" }, { "family_name": "Smyth", "given_name": "Padhraic", "clpid": "Smyth-P" }, { "family_name": "Fayyad", "given_name": "Usama M.", "clpid": "Fayyad-U-M" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Humans can look at a scene or a photograph and easily recognize objects. Outside my window I can see cars, people walking a dog on a brick pathway, trees, buildings, etc. This perception is so effortless that it belies the difficulty of the task. Visual perception begins with light that is reflected from the scene into the eye. The light impinges upon the retina and is transduced by a two-dimensional array of photoreceptors into noisy electrical signals. The brain must then accomplish the difficult task of transforming from this low-level representation to a higher-level understanding of the scene in terms of regions, surfaces, textures, and objects.
\r\n\r\nFor computer vision the problem is the same, but the hardware is different. A camera approximates the function of the eye and retina; that is, the camera produces a two-dimensional array of numbers (pixel values) representing the intensity of light reflected from the scene. The fundamental question addressed in this thesis is the following: what mathematical processing should be applied to the pixel values in order for a computer to recognize objects? The methods we propose are not intended as a model of human brain function, although they may provide some insight. We are simply trying to solve the same visual recognition problems as the brain without concern for whether (or how) our algorithms could be realized in neuronal \"hardware.\"
\r\n\r\nWe have developed a new framework for recognizing visual object classes in which the class members consist of characteristic parts in a deformable spatial configuration. Human faces are an object class of this type, since faces consist of eyes, nose, and mouth arranged in a configuration that varies depending on expression and pose and also from one person to another. A second object class is cursive handwriting, which consists of loops, cusps, crossings, etc. arranged in a deformable pattern. In our approach, the allowed object deformations are represented through shape statistics, which are learned from examples. Instances of an object in an image are detected by finding the appropriate features in the correct spatial configuration. Our algorithm is robust with respect to partial occlusion, detector false alarms, and missed features.
\r\n\r\nPotential applications include intelligent tools for finding objects in image data-bases, human-machine interfaces, user authentication, intelligent data gathering and compression, signature verification, and keyword spotting. Experimental results will be presented for two problems: (1) locating quasi-frontal views of human faces in cluttered scenes and with occlusions and (2) spotting keywords in on-line cursive handwriting data.
", "doi": "10.7907/96P7-6E62", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:88", "collection": "thesis", "collection_id": "88", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01092008-080326", "primary_object_url": { "basename": "Diorio_c_1997.pdf", "content": "final", "filesize": 7046636, "license": "other", "mime_type": "application/pdf", "url": "/88/1/Diorio_c_1997.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Neurally Inspired Silicon Learning : from Synapse Transistors to Learning Arrays", "author": [ { "family_name": "Diorio", "given_name": "Christopher J.", "clpid": "Diorio-Christopher-J" } ], "thesis_advisor": [ { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" } ], "thesis_committee": [ { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A computation is an operation that can be performed by a physical machine. We are familiar with digital computers: Machines based on a simple logic function (the binary NOR) and optimized for manipulating numeric variables with high precision. Other computing machines exist: The neurocomputer, the analog computer, the quantum computer, and the DNA computer all are known. Neurocomputers-defined colloquially as computing machines comprising nervous tissue-exist; that they are computers also is certain. Nervous tissue solves ill-posed problems in real time. The principles underlying neural computation, however, remain for now a mystery.\r\n\r\nI believe that there are fundamental principles of computation that we can learn by studying neurobiology. If we can understand how biological information-processing systems operate, then we can learn how to build circuits and systems that deal naturally with real-world data. My goal is to investigate the organizational and adaptive principles on which neural systems operate, and to build silicon integrated circuits that compute using these principles. I call my approach silicon neuroscience: the development of neurally inspired silicon-learning systems.\r\n\r\nI have developed, in a standard CMOS process, a family of single-transistor devices that I call synapse transistors. Like neural synapses, synapse transistors provide nonvolatile analog memory, compute the product of this stored memory and the applied input, allow bidirectional memory updates, and simultaneously perform an analog computation and determine locally their own memory updates. I have fabricated a synaptic array that affords a high synapse-transistor density, mimics the low power consumption of nervous tissue, and performs both fast, parallel computation and slow, local adaptation. Like nervous tissue, my array simultaneously and in parallel performs an analog computation and updates the nonvolatile analog memory.\r\n\r\nAlthough I do not believe that a single transistor can model the complex behavior of a neural synapse completely, my synapse transistors do implement a local learning function. I consider their development to be a first step toward achieving my goal of a silicon learning system.\r\n", "doi": "10.7907/vbyq-fy15", "publication_date": "1997", "thesis_type": "phd", "thesis_year": "1997" }, { "id": "thesis:2477", "collection": "thesis", "collection_id": "2477", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06062005-155140", "primary_object_url": { "basename": "Hasler_p_1997.pdf", "content": "final", "filesize": 8386714, "license": "other", "mime_type": "application/pdf", "url": "/2477/1/Hasler_p_1997.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Foundations of learning in analog VLSI", "author": [ { "family_name": "Hasler", "given_name": "Paul Edward", "clpid": "Hasler-Paul-Edward" } ], "thesis_advisor": [ { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" } ], "thesis_committee": [ { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Andreou", "given_name": "Andreas G.", "orcid": "0000-0003-3826-600X", "clpid": "Andreou-Andreas-G" }, { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "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\nFloating-gate technology can be used to build silicon systems that adapt and learn. This technology is well suited to implement adaptation and learning because we are not building analog EEPROMS, but rather circuit elements with important time domain dynamics. These floating-gate circuits use the hot-electron-injection, electron-tunneling, and drain-induced-barrier-lowering phenomena in a standard submicron CMOS process. This technology works with the constraints of the silicon medium, and is similar to biological systems that turned potential liabilities into features.\r\n\r\nI develop the first analytical model of the impact-ionization and hot-electron processes in MOS devices by solving for a self-consistent distribution function from the spatially varying Boltzmann transport equation. From this electron distribution function, the probabilities of impact ionization and hot-electron injection are calculated as functions of channel current, drain voltage, and floating-gate voltage. The analytical model simultaneously fits both the hot-electron-injection and impact-ionization data. These analytical results yield measurements of the energy-dependent impactionization collision rate that is consistent with numerically calculated collision rates reported in the literature.\r\n\r\nI describe the design, fabrication, characterization, and modeling of an array of single-transistor synapses that simultaneously store the weight value, compute the product of the input and floating gate value, and update the weight value according to a hebbian or backpropagation learning rule. Circuits with one floating-gate synapse exhibit a range of possible stabilizing and destabilizing behaviors, and circuits with multiple-synapses show examples of competitive and cooperative behavior. By providing feedback to the source, we get a [...]FET synapse where voltage changes in both the floating gate and drain stabilize the floating gate.\r\n\r\nI present a bandpass floating gate amplifier that uses tunneling and [...]FET hot-electron injection to adaptively set its DC operating point. Because the gate currents are small, the circuit exhibits a high-pass characteristic with a cutoff frequency less than 1 Hz. The high frequency cutoff is controlled electronically, as is done in continuous-time filters. I have derived analytical models that completely characterize the amplifier and that are in good agreement with experimental data for a wide range of operating conditions and input waveforms. This autozeroing floating-gate amplifier demonstrates how to use continuous-time, floating-gate adaptation.", "doi": "10.7907/2J7M-GE02", "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:789", "collection": "thesis", "collection_id": "789", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02272008-130211", "primary_object_url": { "basename": "Burr_gw_1996.pdf", "content": "final", "filesize": 33884817, "license": "other", "mime_type": "application/pdf", "url": "/789/1/Burr_gw_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Volume holographic storage using the 90\u00b0 geometry", "author": [ { "family_name": "Burr", "given_name": "Geoffrey W.", "clpid": "Burr-G-W" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nVolume holographic data storage involves the superposition and independent recall of multiple pages of data within the same volume of a storage medium. These pages, stored as separate holograms, can be accessed by changing the angle of the reference laser beam used to store and retrieve them. Because all the data in a stored page is read out in parallel, the output data rate can be very large. At the same time, large storage capacity is available through the superposition of many data pages.\n\nThe topic of this thesis is volume holographic memories using the 90\u00b0 geometry. This configuration, where signal and reference beams enter orthogonal crystal faces, is attractive for angle multiplexing because of its high angular selectivity. We choose angle multiplexing because it gives us many options for rapid steering of the reference beams. Our goal is to develop read\u2014write holographic memories which achieve high capacity and high output data rate.\n\nOur approach, in terms of recording material, is to work with what we have. In our case, the only photorefractive widely available in thicknesses greater than a centimeter is Fe-doped [...]. This material is relatively easy to make with high optical quality, and its performance shows no degradation after repeated record/thermal erase cycles. The disadvantages of [...]Fe include volatility of storage, which we will treat briefly, and poor dynamic range, which we will discuss extensively in the first part of the thesis. We start in Chapter 2 with a study of dynamic range in holographic storage, in order to determine what is required of a photorefractive crystal. One of the outcomes of this study is a concise metric\u2014which we call the M/#\u2014for measuring the dynamic range performance of a holographic storage system. Chapter 3 discusses the experimental measurement of this M/# as a function of the oxidation state of [...]. We find that there exists an optimal oxidation state (for maximum dynamic range performance), and in Chapter 4 we develop a theoretical model which predicts this optimum. In the remainder of Chapter 4, we extend this model to other parameters such as crystal size, doping, and modulation depth.\n\nHaving squeezed as much performance as possible from our storage material, we turn to the design of a large\u2013scale holographic memory. Our goal is to use angle, fractal, and spatial multiplexing to achieve large capacity\u2014without sacrificing fast access to the stored holograms. In Chapter 5, we discuss our segmented mirror array, and how it makes such a design possible. Then in Chapter 6, we experimentally demonstrate the various features of this memory design. These demonstrations include storage using the mirror array, storage of 1000 holograms using an acousto\u2013optic deflector, storage of 10,000 holograms in the same [...] volume of [...], and the demonstration of the 160,000 hologram system with the mirror array and mechanical scanners.\n\nIn this last part of the thesis, we consider additional aspects of holographic storage, in preparation for proposing a bigger and better system. In Chapter 7, we discuss systems issues affecting holographic memory design. In this vein, we survey the methods of performing angle\u2013multiplexing, and introduce and demonstrate a new device for angle steering: a silicon bulk\u2013micromachined, magnetically\u2013actuated micromirror. We also discuss time response and noise and error performance of holographic memories. Finally, in Chapter 8 we propose and discuss several next\u2013generation designs for large\u2013scale high\u2013speed holographic memories. This includes a method for nonvolatile readout that combines several previously proposed methods.\n", "doi": "10.7907/0vbj-pb92", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:1560", "collection": "thesis", "collection_id": "1560", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05012006-124513", "primary_object_url": { "basename": "Luo_J_1996.pdf", "content": "final", "filesize": 11186591, "license": "other", "mime_type": "application/pdf", "url": "/1560/1/Luo_J_1996.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Monolithic GaAs VLSI optoelectronic neuron arrays", "author": [ { "family_name": "Luo", "given_name": "Jiafu", "clpid": "Luo-Jiafu" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Corngold", "given_name": "Noel Robert", "clpid": "Corngold-N-R" }, { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis focuses on the design and fabrication of GaAs monolithic optoelectronic integrated circuits (OEIC's) for use in optical neural networks. The basic circuit in a neuron array consists of GaAs MESFET (Metal-Semiconductor Field Effect Transistor) circuits and optical input/output (I/O) devices. By implementing the I/O process optically, we can greatly increase the neuron density for a 2-dimensional array and thus achieve highly parallel computation.\r\n\r\nBecause of the high loss involved in optical interconnections, high density neuron arrays require high gain photodetectors and high efficiency output devices. With responsivities up to 10(4)A/W and structure compatibility with MESFET circuits, optical FET detectors (OPFET's) are an excellent choice as photodetectors. Several techniques have been investigated in order to fabricate high efficiency LED's (light-emitting-diodes) at low current levels. Low power consumption neurons based on OPFET's and GaAs/A1GaAs double-Zn-diffusion double-heterojunction LED's are fabricated using in-house facilities.\r\n\r\nIndustrial foundries provide the most convenient answer to the challenge of fabricating high density 2-D neuron arrays. Two approaches will be described. The first approach utilizes the FET-SEED (self-electrooptic effect device) process from AT&T Bell labs. It provides monolithically integrated circuits with optical I/O devices and depletion mode FET's. In the other approach, GaAs/AlGaAs multiple quantum well modulators are grown on MOSIS GaAs MESFET circuits by MBE regrowth. It is found that in both approaches, the FET's can be used as high gain photodetectors even though the mechanisms are different, thus making it possible to achieve low power consumption high density neuron arrays. Various kinds of complex optoelectronic circuits can be fabricated through these two approaches.", "doi": "10.7907/F7DG-YM82", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:3542", "collection": "thesis", "collection_id": "3542", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09142006-154808", "primary_object_url": { "basename": "Marx_ds_1996.pdf", "content": "final", "filesize": 23944447, "license": "other", "mime_type": "application/pdf", "url": "/3542/1/Marx_ds_1996.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Subwavelength structures, optical diffraction, and optical disc memories", "author": [ { "family_name": "Marx", "given_name": "David Solomon", "clpid": "Marx-D-S" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "Conventional optical memory discs store information in the form of pits embossed on the disc. The minimum size of the pit marks is limited by the resolution of the optical system used to read the disc. Our investigations, presented in this thesis, are primarily concerned with the question, \"Can an optical disc memory be designed so that an optical system can recover information from symbols (pit marks or otherwise) which are normally unresolved?\" When an optical system can determine unresolved features of an object, then superresolution has been accomplished.\n\nWe describe an experiment to recover information about lines with a width one fifth the minimum resolvable feature size. The result uncovers an important difference between an optical memory and a classical optical imaging system: in an optical memory, we can use a priori information about the finite number of possible stored states. The next investigation is for superresolution in depth, rather than for a lateral direction. We select the method of conoscopic holography and demonstrate the ability to measure the depth of a reflecting surface with an accuracy better than one-tenth the depth of focus of the optical system.\n\nTo allow the design and analysis of a memory format, we formulate an integral method to calculate diffraction for large numerical aperture focused beams on nonperiodic two-dimensional structures. The numerical method is tested for numerical convergence and accuracy, and some comparisons of numerical results and experimental measurements are also shown. We then use the numerical method extensively to analyze a variety of formats and structures.", "doi": "10.7907/9a76-bg20", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:2514", "collection": "thesis", "collection_id": "2514", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06082005-110714", "primary_object_url": { "basename": "Orlov_ss_1996.pdf", "content": "final", "filesize": 6033886, "license": "other", "mime_type": "application/pdf", "url": "/2514/1/Orlov_ss_1996.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Holographic storage dynamics, phase conjugation, and nonlinear optics in photorefractive materials", "author": [ { "family_name": "Orlov", "given_name": "Sergei S.", "clpid": "Orlov-S-S" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Perona", "given_name": "Pietro", "clpid": "Perona-P" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis explores the application of photorefractive materials in two distinct areas: the holographic data storage and the dynamic nonlinear optical interactions. First, we have established that partial ferroelectric domain reversal in certain ferroelectric materials can be used to permanently fix the dynamic holographic gratings, and analyzed the interaction between the fixed and the dynamic components of a hologram. A comprehensive analysis of the storage temporal dynamics in photorefractive materials is further developed for the case of thermal ionic fixing. An experimental study of holographic storage dynamics in photorefractive lithium niobate revealed new features related to the ionic conductivity in this and similar materials. We established and developed techniques for long-lifetime and high-efficiency hologram fixing in the holographic data storage applications. We further analyze theoretically the impact of the recording response properties of different storage media (including photorefractive materials and photopolymers) and optical detection noise on the ultimate storage capacity of holographic memories.\n\nSecond, the transverse properties of the photorefractive double phase conjugate mirror (DPCM) have been studied. We have established that the DPCM exhibits a sharp conjugation fidelity gain threshold which increases with image resolution, while the reflectivity is a smoothly varying function of nonlinear gain. The conjugation fidelity was found to degrade dramatically for unequal intensities ratio. The DPCM exhibits critical slowing down in the vicinity of the oscillation threshold. A two-dimensional coupled-modes perturbation analysis of the DPCM is introduced and its basic predictions are in a good qualitative agreement with the results of the experimental study.\n\nFinally, we analyze the nonlinear optical second harmonic generation in materials with strong photorefractivity. In the presence of strong self-phase modulation the phase matching conditions are modified and we found that in some cases this leads to a unique effect, namely, the nonlinear self-phase matching of optical nonlinear interaction. Strong photorefractive response manifests itself in two characteristic and very apparent manners; a large change in the conversion efficiency and self-defocusing of the generated second harmonic beam. We introduced a two-dimensional model of photorefractive effect and found its predictions to be in a good qualitative agreement with the observed transverse dynamics.\n", "doi": "10.7907/RYVB-3254", "publication_date": "1996", "thesis_type": "phd", "thesis_year": "1996" }, { "id": "thesis:684", "collection": "thesis", "collection_id": "684", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02202004-150303", "primary_object_url": { "basename": "Cortese_ja_1995.pdf", "content": "final", "filesize": 6621773, "license": "other", "mime_type": "application/pdf", "url": "/684/1/Cortese_ja_1995.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Stochastic Computation", "author": [ { "family_name": "Cortese", "given_name": "John Anthony", "clpid": "Cortese-John-Anthony" } ], "thesis_advisor": [ { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" } ], "thesis_committee": [ { "family_name": "Franklin", "given_name": "Joel N.", "clpid": "Franklin-J-N" }, { "family_name": "Simon", "given_name": "Marvin K.", "clpid": "Simon-M-K" }, { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis approaches computation from a communication theory perspective. Data is given to a computer, which is asked to arrive at a binary hypothesis decision. The computation task is viewed as a signal drawn from an ensemble, corrupted by noise, and passed to a receiver which is asked to make a binary signal detection decision.
\r\n\r\nTo illustrate the approach, learning in a neural network is studied. An algorithm based on statistical communication techniques is developed which allows the determination of the neural network size, architecture, and system parameters. The computation, as interpreted in the communication framework, is assigned an equivalent channel capacity which measures the effectiveness with which the computing system extracts information in the Shannon sense from the input data. Numerical simulations of a neural network recognizing handwritten digits are used to illustrate key points.
", "doi": "10.7907/W627-YA05", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:4101", "collection": "thesis", "collection_id": "4101", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10152007-133745", "primary_object_url": { "basename": "Levy_hj_1995.pdf", "content": "final", "filesize": 4011064, "license": "other", "mime_type": "application/pdf", "url": "/4101/1/Levy_hj_1995.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Application and integration of quantum-effect devices for cellular VLSI", "author": [ { "family_name": "Levy", "given_name": "Harold", "clpid": "Levy-H" } ], "thesis_advisor": [ { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" } ], "thesis_committee": [ { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Cellular VLSI is that subclass of electronic systems for which small perturbations in a repeated cell design can dramatically influence the cost and performance of the entire system. This thesis presents examples of how the room-temperature quantum effects of tunneling and resonance may be used to condense the functionality of many conventional VLSI devices into a smaller and more efficient subunit, thus yielding tremendous benefits for the system as a whole. In particular, two and three-terminal applications of a complimentary pair of quantum-effect devices, the resonant-tunneling diode and the tunneling-switch diode, are presented.\r\n\r\nThe first example is an image-segmentation network for machine vision, implemented by using resonant-tunneling diodes in one and two-dimensional networks to extract boundaries between regions of constant spatial texture. In this case a single quantum-effect device may replace up to thirty-three CMOS transistors per pixel.\r\n\r\nThe second example is an artificial neural-network processor based on multistate resistors for synaptic conductances. These programmable resistors were produced by combining a vertically-integrated stack of resonant-tunneling diodes with a resistive load and a single MOSFET driven in its ohmic region. This macrostructure has the potential to provide synaptic changes on the picosecond time scale at length scales well below one micron.\r\n\r\nThe third example is a current-mode transistorless memory array based on a two-dimensional network of cells containing only a single tunneling-switch diode and a resistive load. The resulting system has the potential for reaching more than an order-of-magnitude more cell density than state-of-the-art DRAM arrays, while operating at state-of-the-art SRAM speeds and reasonable power consumption.", "doi": "10.7907/qtd4-5r46", "publication_date": "1995", "thesis_type": "phd", "thesis_year": "1995" }, { "id": "thesis:817", "collection": "thesis", "collection_id": "817", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03012004-161831", "primary_object_url": { "basename": "Li_hys_1994.pdf", "content": "final", "filesize": 8033993, "license": "other", "mime_type": "application/pdf", "url": "/817/1/Li_hys_1994.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Photorefractive 3-D disks for optical data storage and artificial neural networks", "author": [ { "family_name": "Li", "given_name": "Hsin-Yu Sidney", "clpid": "Li-H-S" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "This thesis is on the application of 3-D photorefractive crystals disks for holographic optical data storage and optical neural networks.\r\n\r\nChapter 1 gives some introductory background and motivation for the materials given in this thesis. In Chapter 2, the coupled-mode analysis and Born's approximation in anisotropic crystals is reviewed. The results are similar to that of isotropic materials. However, there are approximations that are often neglected in the literature.\r\n\r\nChapter 3 starts with the description of the holographic 3-D disk for data storage, and analyzes the various alignment errors and tolerance problems for a 3D disk system. Of particular interest is the effects in image reconstruction caused by rotational angle error. An optimum configuration is found that minimizes this error.\r\n\r\nChapter 4 examines the data storage density of 3-D disks and volume holographic storage systems that utilize wavelength/angle and spatial multiplexing. The maximum storage density and the geometry that achieves this density is derived.\r\n\r\nChapter 5 discusses the diffraction efficiency of 3-D disks fabricated with photorefractive crystals. Practical geometries and crystal orientations for achieving maximum uniform diffraction efficiency are given and compared to the maximum obtainable diffraction efficiencies using arbitrary cut crystals. Experimental results are shown.\r\n\r\nAlso derived in this chapter are the double grating effect from crystal anisotropy, and the optimum configuration for getting maximum diffraction efficiency using the 90 degree recording geometry. The Kuhktarev band-transport model of the photorefractive effect is examined briefly with emphasis on the anisotropy of the material. The proper expression for the permittivity term in the space-charge field formula is derived.\r\n\r\nChapter 6 gives an example of an optical neural network that uses photorefractive crystals. It is the real time face-recognition system. The setup and experiments are described. Some properties of volume holographic correlators are given in the Appendix.", "doi": "10.7907/wx1q-v852", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:4696", "collection": "thesis", "collection_id": "4696", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11302007-082621", "primary_object_url": { "basename": "Grot_ac_1994.pdf", "content": "final", "filesize": 5964387, "license": "other", "mime_type": "application/pdf", "url": "/4696/1/Grot_ac_1994.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Analog GAAS optoelectronic integrated circuits for large scale arrays", "author": [ { "family_name": "Grot", "given_name": "Annette C.", "clpid": "Grot-A-C" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "This thesis focuses on the design and fabrication of large arrays of analog optoelectronic circuits where transistors and optoelectronic devices such as photodetectors and LEDs are monolithically integrated on a single substrate. This optoelectronic approach allows one to design complex functions with the transistors and use the optoelectronic devices to couple the optical signals in and out of the circuit.\n\n The specific application for the analog optoelectronic circuits is large scale neuron arrays for optical neural networks. A neural network has two main elements: nonlinear elements (neurons) and interconnections (synapses). The neurons perform a nonlinear operation on their incoming signals while the synapses provide the weighted connection between neurons. In an optical neural network, the neurons are arranged as two-dimensional arrays that are optically interconnected using the third dimension.\n\nTwo approaches to the design and fabrication of a variety of optoelectronic GaAs neuron circuits will be described. In the first approach, GaAs MESFETs (Metal-Semiconductor-Field-Effect Transistors), double hetero-structure GaAs/A1GaAs LEDs, and photodetectors are fabricated on a GaAs substrate containing epitaxial layers for the different devices. In the other approach, the detector/transistor portion of the circuit is fabricated by Vitesse through MOSIS and the LEDs are integrated afterwards using MBE regrowth. This second approach produces circuits with high uniformity and allows one to fabricate more complex optoelectronic circuits at a reasonable cost and turn-around-time. Most of the circuits are based on high responsivity optical FET detectors, which make it possible to build high optical gain circuit with little electrical power dissipation and small surface area.", "doi": "10.7907/dz82-bp59", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:4127", "collection": "thesis", "collection_id": "4127", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10172005-130626", "primary_object_url": { "basename": "Rakshit_s_1994.pdf", "content": "final", "filesize": 11540619, "license": "other", "mime_type": "application/pdf", "url": "/4127/1/Rakshit_s_1994.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Analysis of image sequences using redundant representations", "author": [ { "family_name": "Rakshit", "given_name": "Subrata", "clpid": "Rakshit-S" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "This thesis focuses primarily on two techniques often used for low level analysis of motion in image sequences, the computation of optical flow fields and the determination of the spatio-temporal frequencies present. The complexity, cost and accuracy of image sequence processing is shown to be related to the manner in which the information is represented. The optical flow problem is formulated in terms of the basis functions underlying the discrete representation of images. Besides giving good results for a wide variety of inputs, this formalism highlights the benefits of a redundant representation of the input image in terms of reducing the overall cost of analysis. The spatio-temporal filter banks are analyzed using information theory. This approach makes explicit use of the input prior and provides an objective way of comparing the cost effectiveness of filter banks of different sizes. The output is used to generate a probability distribution over selected parameters in order to provide higher visual modules with a richer input. The formalism developed here provides a means of measuring the redundancy in filter bank outputs. This redundancy is shown to provide robustness to noise within the system. Likewise, a redundant representation of the image can also be used for error correction in case of corruption during storage or transmission. An algorithm for using the Burt Laplacian pyramid for such error correction is also developed and demonstrated.", "doi": "10.7907/6vw2-a361", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:4132", "collection": "thesis", "collection_id": "4132", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10172005-155528", "primary_object_url": { "basename": "Curtis_kr_1994.pdf", "content": "final", "filesize": 9316869, "license": "other", "mime_type": "application/pdf", "url": "/4132/1/Curtis_kr_1994.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "3-D photopolymer disks for correlation and data storage, and cross-talk in volume holographic memories", "author": [ { "family_name": "Curtis", "given_name": "Kevin R.", "clpid": "Curtis-K-R" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Grubbs", "given_name": "Robert H.", "clpid": "Grubbs-R-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis considers the optical storage and processing of data using volume holography. First, cross-talk noise due to geometrical considerations is calculated for volume holographic memories. Cross-talk is due to energy diffracted from non-Bragg matched gratings. The SNR (signal-to-noise-ratio) of holographic memories due to cross-talk noise is calculated for Fourier transform holograms stored by angle, wavelength, phase-coded, and rotational multiplexing methods. Considerations include page size, geometry, angular bandwidth of the optical system, wavelength of the light used, material size, spatial light modulator (SLM) contrast, and the phase of the image plane. The SNR for angle multiplexed image plane holograms is also calculated and compared to the results for Fourier transformed angle multiplexed holograms. A comparison of the various multiplexing methods based on cross-talk is presented, and then the effect of geometry and material dynamic range is included to determine when cross-talk will be the dominant noise source. The use of photopolymers as a holographic element is then presented. The recording characteristics of the DuPont photopolymer are described and a method of multiplexing multiple holograms in the photopolymer is given. A new method for multiplexing holograms (called peristrophic multiplexing) is described. This method significantly increases the storage capacity of thin films. After this, a 3-D disk-based correlator and storage device using the photopolymer is described and demonstrated. In this device, holograms are multiplexed at a given spot and then disk rotation/head motion are used to access multiple spots on the disk. Theoretical correlation speed, read-out rates, and the storage capacity of the 3-D disk as limited by geometry and laser power are given.\n", "doi": "10.7907/6FK7-Z369", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:4174", "collection": "thesis", "collection_id": "4174", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10192005-104013", "primary_object_url": { "basename": "Greenspan_h_1994.pdf", "content": "final", "filesize": 15427404, "license": "other", "mime_type": "application/pdf", "url": "/4174/1/Greenspan_h_1994.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Multi-resolution image processing and learning for texture recognition and image enhancement", "author": [ { "family_name": "Greenspan", "given_name": "Hayit", "clpid": "Greenspan-Hayit" } ], "thesis_advisor": [ { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" } ], "thesis_committee": [ { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" }, { "family_name": "Anderson", "given_name": "Charles Hammond", "clpid": "Anderson-C-H" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "A general recognition framework is presented that consists of multi-resolution pyramidal feature-extraction and learning paradigms for classification. The system is presented in the context of the texture recognition task.\r\n\r\nIn the feature extraction part of the system, an oriented Laplacian pyramid is used as an efficient filtering scheme to transform the input image to a more robust representation in the frequency and orientation space. An optimal technique is presented for computing a steerable representation of the pyramid. Steerability is used to generate a rotation-invariant input representation.\r\n\r\nIn the learning stage of the system we focus on a rule-based probabilistic learning scheme. This information-theoretic technique is utilized to find the most informative correlations between the attributes and the output classes while producing probability estimates for the outputs. Both unsupervised and supervised learning are utilized. Apart from the rule-based approach we experiment with other non-parametric classifiers, such as the k-nearest neighbor classifier and the Backprop neural-network.\r\n\r\nWe demonstrate experimentally that our scheme improves significantly upon the state-of-the-art both in rotation-invariant classification and in orientation estimation. A variety of applications are presented, including autonomous navigation scenarios and remote-sensing, as possible extensions for the texture recognition system. A generalization of the system to face-recognition is discussed.\r\n\r\nIn the latter part of the thesis, a procedure for creating images with higher resolution than the sampling rate would allow is described. The enhancement algorithm augments the frequency content of the image by using a non-linearity that generates phase-coherent higher harmonics. The procedure utilizes the Laplacian pyramid image representation. Results are presented depicting the power-spectra augmentation and the visual enhancement of several images. Simplicity of computations and ease of implementation allow for real-time applications such as high-definition television (HDTV). An initial investigation is pursued to combine the enhancement scheme with pyramid coding schemes.", "doi": "10.7907/KR83-J714", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:4173", "collection": "thesis", "collection_id": "4173", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-10192005-081338", "primary_object_url": { "basename": "Cauwenberghs_g_1994.pdf", "content": "final", "filesize": 9303514, "license": "other", "mime_type": "application/pdf", "url": "/4173/1/Cauwenberghs_g_1994.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Analog VLSI Autonomous Systems for Learning and Optimization", "author": [ { "family_name": "Cauwenberghs", "given_name": "Gert", "clpid": "Cauwenberghs-Gert" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Baldi", "given_name": "Pierre", "clpid": "Baldi-Pierre" }, { "family_name": "Barr", "given_name": "Alan H.", "clpid": "Barr-A-H" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The integration of adaptive functions within analog neural hardware, while certainly promising to enhance system performance, has for long been hindered by technological difficulties due to the complexity and sensitivity of standard adaptive algorithms. We present a general framework for self-contained adaptation in analog VLSI supporting a broad class of supervised learning and optimization tasks, which largely alleviates the implementation problems by virtue of a robust system approach exploiting statistics and redundancy in stochastic processes. Specifically, the framework includes: i) a perturbative algorithm based on stochastic approximation to optimize a set of parameters in an arbitrary deterministic system, these parameters being adjusted according to global performance evaluations rather than using explicit knowledge about the internal structure of the system; and ii) a scalable and modular CMOS architecture that implements this algorithm, and that additionally provides for embedded long-term dynamic storage of the volatile analog parameter values, quantized locally and refreshed autonomously on capacitors with direct external access in both digital and analog formats. We analyze the convergence and scaling properties of the stochastic algorithm, present on-line versions of the algorithm for supervised learning in dynamical systems, and provide experimental results demonstrating real-time trajectory learning on an analog CMOS chip containing a network of six fully recurrent dynamical neurons. We also include results demonstrating robust long-term retention of locally stored volatile information in analog VLSI using the autonomous refresh technique.", "doi": "10.7907/CW78-8H63", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:4781", "collection": "thesis", "collection_id": "4781", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12042007-084534", "primary_object_url": { "basename": "Qiao_y_1994.pdf", "content": "final", "filesize": 6407644, "license": "other", "mime_type": "application/pdf", "url": "/4781/1/Qiao_y_1994.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Learning dynamics of photorefractive neural networks", "author": [ { "family_name": "Qiao", "given_name": "Yong", "clpid": "Qiao-Y" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.\n\nThis thesis investigates the optical implementation of neural networks utilizing dynamic photorefractive volume holography. The number of accessible degrees of freedom in a general holographic interconnection system is derived, and a cascaded-grating scheme that provides full, nondegenerate interconnections between two unsampled planes is presented. The dynamics of the formation of photorefractive volume holograms is considered. The impact of time-constant asymmetry on multiple hologram recording is evaluated. A basic framework for controlling the dynamics of photorefractive holograms is described and a number of dynamic copying methods for rejuvenating decayed holograms are identified. Experiments of linear dynamic copying using phase conjugation and nonlinear copying using an optical feedback loop are presented. The electrical fixing of photorefractive holograms in [...] crystals is experimentally demonstrated and the physical mechanism is discussed. A number of neural learning algorithms are investigated for optical implementation. An Anti-Hebbian local learning algorithm is proposed to simplify the optical architecture of feedforward multilayer networks. Experimental demonstrations of several optical neural networks are presented. An optical perceptron is trained for face classification, and the use of dynamic copying for improving its performance is demonstrated. A two-layer network based on Kanerva's sparse, distributed memory model is implemented and trained for real-time handwritten character recognition. Finally an optical two-layer network for real-time face recognition, with moderate tolerance to shift, rotation, scale, and facial expression, is presented.\n", "doi": "10.7907/5qwx-ww61", "publication_date": "1994", "thesis_type": "phd", "thesis_year": "1994" }, { "id": "thesis:3303", "collection": "thesis", "collection_id": "3303", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08312007-094832", "primary_object_url": { "basename": "Neugebauer_cf_1993.pdf", "content": "final", "filesize": 4822520, "license": "other", "mime_type": "application/pdf", "url": "/3303/1/Neugebauer_cf_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Parallel Analog Computation with Charge Coupled Devices", "author": [ { "family_name": "Neugebauer", "given_name": "Charles F.", "clpid": "Neugebauer-Charles-F" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Many signal processing and neural network algorithms can be mathematically described in terms of vector matrix multiplication. This thesis introduces two new architectures for computing high-speed vector matrix multiplication using charge coupled devices. These integrated circuits have been designed to accept optical matrix input as well as direct electrical matrix input. In both architectures, the matrix elements are stored as analog charge packets in CCD wells while the vectors are communicated to and from the integrated circuits by electrical means.\r\n\r\nThe first architecture accomplishes the vector matrix product using a semiparallel computation scheme that requires N clock cycles of the device to complete one vector matrix multiplication where N is the length of the input vector. An analysis of the linearity and charge transfer induced errors is given. The circuit represents an advance over other analog signal processors in density and speed but has serious shortcomings in accuracy, particularly the limited precision of the input vectors.\r\n\r\nThe second architecture is based on charge injection device (CID) imager arrays and addresses many of the inadequacies of the semiparallel architecture. A fully parallel circuit, the CID has similar density and much higher computation speed and accuracy. A novel digital input method is introduced that extends the input vector precision significantly. In addition, accuracy issues related to charge transfer efficiency are resolved. An analysis of linearity and accuracy is provided showing the advantages of the architecture over previous implementations.", "doi": "10.7907/3e7h-9p50", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:3269", "collection": "thesis", "collection_id": "3269", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08292007-100152", "primary_object_url": { "basename": "Kerns_da_1993.pdf", "content": "final", "filesize": 3872245, "license": "other", "mime_type": "application/pdf", "url": "/3269/1/Kerns_da_1993.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Experiments in Very Large-Scale Analog Computation", "author": [ { "family_name": "Kerns", "given_name": "Douglas A.", "clpid": "Kerns-Douglas-A" } ], "thesis_advisor": [ { "family_name": "Hopfield", "given_name": "John J.", "clpid": "Hopfield-J-J" } ], "thesis_committee": [ { "family_name": "Hopfield", "given_name": "John J.", "clpid": "Hopfield-J-J" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Pine", "given_name": "Jerome", "clpid": "Pine-J" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The easy and inexpensive availability of microelectronic prototype fabrication allows us to perform many kinds of experiments in the construction of electronic computational machinery. There has been a recent resurgence in analog computation in various guises: electronic implementations of neural networks, other kinds of neuromorphic circuits, and electronic simulations of various physical systems.\r\n\r\nThis text documents a set of experiments in analog computation in silicon, and includes a short discussion of the relative advantages of analog vs digital computation. The most generally useful result of the work is the development of a set of techniques that allow analog circuits to automatically trim themselves, turning marginal components into devices of good precision.", "doi": "10.7907/5ph3-1w81", "publication_date": "1993", "thesis_type": "phd", "thesis_year": "1993" }, { "id": "thesis:3039", "collection": "thesis", "collection_id": "3039", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08072007-133843", "primary_object_url": { "basename": "Lin_sh_1992.pdf", "content": "final", "filesize": 10394982, "license": "other", "mime_type": "application/pdf", "url": "/3039/1/Lin_sh_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "GaAs optoelectronic integrated circuits for optical neural network applications", "author": [ { "family_name": "Lin", "given_name": "Steven H.", "clpid": "Lin-S-H" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "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": "Optoelectronic integrated circuits (OEIC's) have emerged as a viable method in the implementation of optical neurons required for a neural network. This is due to the increased capability in both the material and the device engineering in GaAs technology, which has proliferated incredibly fast during the last decade. In this thesis, two different approaches to monolithically integrate various electronic and optical devices are explored for the implementation of optical neurons. The first approach utilizes the technology from double heterojunction bipolar transistor for its potentially high current gain and its structural compatibility with optical devices. In achieving the current gain required for optical neurons, modeling of the base leakage current, effect of surface passivation and diffusion characteristics is performed for Zn-diffused bipolar transistors. The second approach employs metal semiconductor field-effect transistors as the driver for the optical devices. It is found that, by properly designing the circuit, high optical gain, low electrical power dissipation and low optical switching energy thresholding devices can be accomplished in this approach with large input-output isolation. Such performance is required if large arrays of optoelectronic neurons are to be inserted into a neural network to perform tasks that make neural computation a unique approach in solving a certain class of problems. In this thesis, an optical gain of 80 is demonstrated along with an electrical power dissipation of 1.6 mW and an optical switching energy of 10 pJ. These results generate high promises and optimism for the realization of a physical neural computer in the near future.", "doi": "10.7907/tqm4-en29", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:3173", "collection": "thesis", "collection_id": "3173", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08202007-091426", "primary_object_url": { "basename": "Yamamura_aa_1992.pdf", "content": "final", "filesize": 15876466, "license": "other", "mime_type": "application/pdf", "url": "/3173/1/Yamamura_aa_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Neural network control and an optoelectronic implementation of a multilayer feedforward neural network", "author": [ { "family_name": "Yamamura", "given_name": "Alan Akihiro", "clpid": "Yamamura-Alan-Akihiro" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Sideris", "given_name": "Athanasios", "clpid": "Sideris-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Artificial neural networks are a computational paradigm inspired by biological neural systems. By modeling neural networks to a certain degree after their counterparts in nature, it is hoped that they can capture those aspects of biological neural systems that allow them to outperform more conventional processing systems in tasks such as motor control and pattern recognition. A brief overview of neural networks is provided in Item 1, concentrating on those aspects pertinent to the remainder of this thesis.\r\n\r\nThe application of neural networks to control is examined in Item 2. A general control system can be divided into feedforward and feedback components. Specifically, the use of neural networks in learning to generate the feedforward control signal for unknown, potentially nonlinear, plants is examined. A class of learning algorithms applicable to feedforward networks is developed, and their use in learning to control a simulated two-link robotic manipulator is studied.\r\n\r\nAn optoelectronic implementation of a multilayer feedforward neural network, with binary weights and connections, is described in the final part of this thesis. The neurons and connections are implemented electronically on a custom VLSI chip. The pattern and strength of the connections is controlled, through photodetectors placed in the connections, by a pattern of light illuminating the chip. This pattern is read out, in parallel, from an optical disk. Issues concerning parallel readout of information from optical disks are discussed in Item 3, while Item 4 contains a descriptionn of both the design of the Optoelectronic Neural Network Chip (ONNC) and experiments involving the optical disk and neural network chip.\r\n", "doi": "10.7907/4dbn-z991", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:2956", "collection": "thesis", "collection_id": "2956", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-07202007-143215", "primary_object_url": { "basename": "c_ji_1992.pdf", "content": "final", "filesize": 3934938, "license": "other", "mime_type": "application/pdf", "url": "/2956/1/c_ji_1992.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Generalization capability of neural networks", "author": [ { "family_name": "Ji", "given_name": "Chuanyi", "clpid": "Ji-Chuanyi" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The generalization capability of feedforward multilayer neural networks is investigated from two aspects: the theoretical aspect and the algorithmic aspect.
\r\n\r\nIn the theoretical part, a general relation is derived between the so-called VC-dimension and the statistical lower epsilon-capacity, and then applied to two cases. First, as a general constructive approach, it is used to evaluate a lower bound of the VC-dimension of two layer networks with binary weights and integer thresholds. Second, how the sample complexity may vary with respect to distributions is investigated through analyzing a particular network which separates two binary clusters. Bounds for the capacity of two layer networks with binary weights and integer thresholds are also obtained.
\r\n\r\nIn the algorithmic part, a network reduction algorithm is developed to study generalization in learning analog mappings. It is applied to control a two-link manipulator to draw characters. The network addition-deletion algorithm is described to find an appropriate network structure during learning. It is used to study the effect of sizes of networks on generalization, and applied to various classification problems including hand written digits recognition.
", "doi": "10.7907/HR3F-0410", "publication_date": "1992", "thesis_type": "phd", "thesis_year": "1992" }, { "id": "thesis:3725", "collection": "thesis", "collection_id": "3725", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09232005-083502", "primary_object_url": { "basename": "Atiya_a_1991.pdf", "content": "final", "filesize": 6103064, "license": "other", "mime_type": "application/pdf", "url": "/3725/1/Atiya_a_1991.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Learning algorithms for neural networks", "author": [ { "family_name": "Atiya", "given_name": "Amir", "clpid": "Atiya-Amir" } ], "thesis_advisor": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "thesis_committee": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis deals mainly with the development of new learning algorithms and the study of the dynamics of neural networks. We develop a method for training feedback neural networks. Appropriate stability conditions are derived, and learning is performed by the gradient descent technique. We develop a new associative memory model using Hopfield's continuous feedback network. We demonstrate some of the storage limitations of the Hopfield network, and develop alternative architectures and an algorithm for designing the associative memory. We propose a new unsupervised learning method for neural networks. The method is based on applying repeatedly the gradient ascent technique on a defined criterion function. We study some of the dynamical aspects of Hopfield networks. New stability results are derived. Oscillations and synchronizations in several architectures are studied, and related to recent findings in biology. The problem of recording the outputs of real neural networks is considered. A new method for the detection and the recognition of the recorded neural signals is proposed.\r\n", "doi": "10.7907/F46C-3V67", "publication_date": "1991", "thesis_type": "phd", "thesis_year": "1991" }, { "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:1707", "collection": "thesis", "collection_id": "1707", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05092007-130540", "primary_object_url": { "basename": "Liu_vct_1990.pdf", "content": "final", "filesize": 4977200, "license": "other", "mime_type": "application/pdf", "url": "/1707/1/Liu_vct_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "One and two-dimensional digital mutirate systems with applications in sub-sampling and bandlimited signal reconstruction", "author": [ { "family_name": "Liu", "given_name": "Vincent Cheng-Teh", "clpid": "Liu-V-C" } ], "thesis_advisor": [ { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" } ], "thesis_committee": [ { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis deals with the two-dimensional (2D) multirate quadrature mirror filter (QMF) bank and new applications of 1D and 2D multirate filter bank concepts to the periodic nonuniform sampling and reconstruction of bandlimited signals. The potential use of multirate filter banks in the statistically optimal estimation of signals in the presence of wide-sense cyclostationary noise is also examined. The two-dimensional QMF bank is free from aliasing if and only if a certain polyphase matrix product related to the filter bank possesses the 2D pseudo-circulant property. A 2D FIR filter bank can be designed with the perfect reconstruction property if the polyphase matrix of its analysis filter bank is constrained to be a 2D lossless matrix. A design example is included. The losslessness constraint is satisfied by imposing a cascaded structure of first-degree lossless sections on the polyphase matrix. A limited factroization theorem is derived for 2D FIR lossless systems where the order in one of the two dimensions is limited to unity. In the area of nonuniform sampling of multiband bandlimited signals, the filter bank approach is utilized to derive a computationally efficient method for reconstructing bandlimited signals. The above scheme can also be viewed as a mean of compressing and reconstructing an oversampled bandlimited signal. It is shown that such a scheme has lower computational complexity than traditional methods of sampling rate alteration. The results can be extended to nonuniform sampling in two-dimensions using integer lattices. A further application of the multirate filter bank is in signal estimation in the presence of cyclostationary noise. The necessary and sufficient condition for the filter bank to preserve the wide-sense stationarity of the input is derived. Several applications where cyclostationary noise is present are indicated, and through the use of simulations the performance of the optimal filter bank can be compared with the conventional scalar optimal filter. The roundoff noise in orthogonal matrix building blocks is analyzed, since these building blocks are commonly present in filter bank implementations.", "doi": "10.7907/cvbb-m844", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:1718", "collection": "thesis", "collection_id": "1718", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05102007-111726", "primary_object_url": { "basename": "Park_ch_1990.pdf", "content": "final", "filesize": 3901058, "license": "other", "mime_type": "application/pdf", "url": "/1718/1/Park_ch_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optical computing and higher order associative memories", "author": [ { "family_name": "Park", "given_name": "Cheol Hoon", "clpid": "Park-C-H" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "Beginning with a discussion of the relationship between degrees of freedom and capacity of the system, the original work on higher order associative memories is described in three aspects, Learning, Capacity, and Generalization for pattern recognition and neural networks with the orthogonalization of binary vectors and the ternarization of weights, and their optical implementations using volume holograms are suggested for optical computing. Selection of terms is considered to satisfy the given conditions. When a simple sum of outer product learning rule is applied, higher order memories become higher order Hopfield-type memories. Their capacities are derived from SNR analyses for both nonzero diagonal and zero diagonal memories. Especially in the case of quadratic and cubic memories, optical implementations are suggested in three elegant ways due to the three-dimensional property of volume holograms. Robustness of higher order associative memories is discussed as a generalization property with consideration of dynamic range in terms of robustness of errors in input (error tolerance) and noise in the system (noise sensitivity). In the case of autoassociation or bidirectional association the energy functions are used to investigate the dynamics that provides a mechanism of escaping the local minima to find global minima.\n\nAlgorithmic aspects and architectures of optical computing are discussed in terms of deterministic and random algorithms.", "doi": "10.7907/n0ke-5a24", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:1614", "collection": "thesis", "collection_id": "1614", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05042007-142242", "primary_object_url": { "basename": "Hsu_ky_1990.pdf", "content": "final", "filesize": 6106253, "license": "other", "mime_type": "application/pdf", "url": "/1614/1/Hsu_ky_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optical neural computing for associative memories", "author": [ { "family_name": "Hsu", "given_name": "Ken Yuh", "clpid": "Hsu-K-Y" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "Optical techniques for implementing neural computers are presented. In particular, holographic associative memories with feedback are investigated. Characteristics of optical neurons and optical interconnections are discussed. An LCLV is used for simulating a 2-D array of approximately 160,000 optical neurons. Thermoplastic plates are used for providing holographic interconnections among these neurons. The problem of degenerate readout in holographic interconnections and the method of sampling grids to solve this problem are presented.\n\nTwo optical neural networks for associative memories are implemented and demonstrated. The first one is an optical implementation of the Hopfield network. It performs the function of auto-association that recognizes 2-D images from a distorted or partially blocked input. The trade-off between distortion tolerance and discrimination capability against new images is discussed. The second optical loop is a 2-layer network with feedback. It performs the function of hetero-association, which locks the recognized input and its associated image as a stable state in the loop. In both optical loops, it is shown that the neural gain and the similarity between the input and the stored images are the main factors that determine the dynamics of the network.\n\nNeural network models for the optical loops are presented. Equations of motion for describing the dynamical behavior of the systems are derived. The reciprocal vector basis corresponding to stored images is derived. A geometrical method is then introduced which allows us to inspect the convergence property of the system. It is also shown that the main factors that determine the system dynamics are the neural gain and the initial conditions.\n\nPhotorefractive holography for optical interconnections and sampling grids for volume holographic interconnections are presented. A periodic copying method for refreshening multiply exposured photorefractive holograms is presented, which allows the hologram to maintain the same diffraction efficiency as that when a single exposure scheme is used. This scheme provides us with the possibility of achieving maximum storage and maximum diffraction efficiency in holographic associative memories.", "doi": "10.7907/9569-w314", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:2310", "collection": "thesis", "collection_id": "2310", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05302007-134330", "primary_object_url": { "basename": "Riza_na_1990.pdf", "content": "final", "filesize": 59625904, "license": "other", "mime_type": "application/pdf", "url": "/2310/1/Riza_na_1990.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Novel acousto-optic systems for spectrum analysis and phased array radar signal processing", "author": [ { "family_name": "Riza", "given_name": "Nabeel Agha", "clpid": "Riza-N-A" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "abstract": "Novel acousto-optic systems for spectrum analysis and phased array radar signal processing are proposed. The pulsed source 2-D multiplicative time and space integrating spectrum analyzer is proposed and experimentally demonstrated. This architecture is simpler, physically smaller, and less sensitive to mechanical vibrations than the pulsed source 2-D additive Mach-Zehnder interferometer based spectrum analyzer. Simple and compact optical disk based systems for 1-D and 2-D spectrum analysis are presented. The high data packing density, angular motion, and parallel read out capability of optical disks is uniquely exploited to generate the very high time bandwidth product reference signals required for temporal spectrum analysis, that are otherwise difficult to generate using electronics. A continuous wave 1-D time integrating disk spectrum analyzer is successfully demonstrated in the laboratory. The limited dynamic range due to huge bias levels in interferometric time integrating processors is alleviated by using photorefractive crystals as real time bias removers. Continuous wave 1-D and 2-D bias free acousto-optic architectures for spectrum analysis are theoretically and experimentally investigated from a systems viewpoint.\n\nSimple, compact, and powerful acousto-optic systems for control and signal processing in phased array radars are proposed that eliminate many system components like phase shifters, mixers, power dividers, and complex antenna feed networks, that are encountered in typical electronically controlled phased array radars. Via a single control parameter, namely frequency, the optical technique provides appropriately phased signals for transmission and reception in phased array antennas. The system is capable of continuous beam scanning, simultaneous multiple beam formation, and multi-target tracking, and can be integrated on a substrate to provide smaller and lighter phased array radars. Also, the system is resistant to electromagnetic interference (EMI), and signal phase shifts are independent of the radar carrier frequency employed. A 1-D linear phased array radar acousto-optic beam steerer is successfully demonstrated in the laboratory, and performance issues such as detector phase sampling error and phase linearity are highlighted. The linear array design is extended to planar and multiple linear arrays.", "doi": "10.7907/t6wf-tt49", "publication_date": "1990", "thesis_type": "phd", "thesis_year": "1990" }, { "id": "thesis:555", "collection": "thesis", "collection_id": "555", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02082007-130728", "type": "thesis", "title": "Binary Correlators for Optical Computing and Pattern Recognition", "author": [ { "family_name": "Mok", "given_name": "Fai Ho", "clpid": "Mok-Fai-Ho" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" }, { "family_name": "Hopfield", "given_name": "John J.", "clpid": "Hopfield-J-J" }, { "family_name": "Sideris", "given_name": "Athanasios", "clpid": "Sideris-A" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The matrix-vector multiplier is an important building block in optical information processing architectures, examples of which are correlators for pattern recognition, associative memories, and neural networks. Such architectures are most suitable for implementation by optics due to the ease in realizing dense interconnections optically. The success of the implementation partially relies on the quality of the SLM used to record the information for processing. Limited dynamic range for the representation of the data recorded is a common drawback suffered by most commercially available devices. In this thesis, the importance of the dynamic range of the device on the performance of the implementation is investigated. The effect of limited dynamic range on the signal to noise ratio, probability of error, capacity, and training of various forms of matrix-vector multipliers are addressed. Through the use of theoretical analyses, computer simulations, and optical experiments, it will be shown that a large dynamic range is not essential in most applications. Specifically, it is shown that only one bit of dynamic range, i.e. two gray levels, for the representation of each data point, results in acceptable loss in performance.
", "doi": "10.7907/dwpt-gn93", "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:7253", "collection": "thesis", "collection_id": "7253", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11052012-093038170", "primary_object_url": { "basename": "Chiueh_td_1989.pdf", "content": "final", "filesize": 18842589, "license": "other", "mime_type": "application/pdf", "url": "/7253/1/Chiueh_td_1989.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Pattern Classification and Associative Recall by Neural Networks", "author": [ { "family_name": "Chiueh", "given_name": "Tzi-Dar", "orcid": "0000-0003-0851-6629", "clpid": "Chiueh-Tzi-Dar" } ], "thesis_advisor": [ { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" } ], "thesis_committee": [ { "family_name": "Goodman", "given_name": "Rodney M.", "clpid": "Goodman-R-M" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The first part of this dissertation discusses a new classifier based on a multilayer feed-forward network architecture. The main idea is to map irregularly-distributed prototypes in a classification problem to codewords that are organized in some way. Then the pattern classification problem is transformed into a threshold decoding problem, which is easily solved using simple hard-limiter neurons. At first we propose the new model and introduce two families of good \"internal representation\" codes. Then some analyses and software simulation concerning the storage capacity of this new model are done. The results show that the new classifier is much better than the classifier based on the Hopfield model in terms of both the storage capacity and the ability to classify correlated prototypes.
\r\n\r\nA general model for neural network associative memories with a feedback. structure is proposed. Many existing neural network associative memories can be expressed as special cases of this general model. Among these models, there is a class of associative memories, called correlation associative memories, that are capable of storing a large number of memory patterns. If the function used in the evolution equation is monotonically nondecreasing, then a correlation associative memory can be proved to be asymptotically stable in both the synchronous and asynchronous updating modes.
\r\n\r\nOf these correlation associative memories, one stands out because of its VLSI implementation feasibility and large storage capacity. This memory uses the exponentiation function in its evolution equation; hence it is called exponential correlation associative memory (ECAM). It is further proved that the storage capacity of ECAM scales exponentially with N (the number of components in memory patterns) when N approaches infinity. A programmable ECAM chip is designed, simulated, fabricated, and then tested. The performance of the ECAM chip is shown to be not much worse than that of a computer-simulated ECAM model in terms of error correcting ability (attraction radius). Finally, the speed of the prototype ECAM chip is demonstrated by employing it to do vector quantization on binary images. And it is found that the ECAM chip can process binary images in real time.
", "doi": "10.7907/pjan-6r82", "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: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:4465", "collection": "thesis", "collection_id": "4465", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11082007-131130", "type": "thesis", "title": "The Critical Points of Poynting Vector Fields", "author": [ { "family_name": "Rizvi", "given_name": "Syed Azhar Abbas", "clpid": "Rizvi-Syed-Azhar-Abbas" } ], "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": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Whitham", "given_name": "Gerald Beresford", "clpid": "Whitham-G-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In a thought provoking paper Maxwell [The Scientific Papers of James Clerk Maxwell, ed. W. D. Niven, vol. 2, 233-240, Dover Publications, New York (1952)] studied the flow of water on the Earth's surface and how this flow is affected by the local geography. His results linking number of hills and lake bottoms to valleys are simple and the conclusions elegant. Critical points such as summits and lake bottoms play a key role in the overall organization and structuring of the flow lines. This is the spirit in which electromagnetic power flow represented by the Poynting vector field (S) is studied in this thesis. The specialized case of a planar S field which arises due to a single electromagnetic field component Ez or Hz is dealt with here in considerable detail.
\r\n\r\nIn order to analyse the behaviour of the flow lines of a plane Poynting vector field in the neighbourhood of a critical point, the S field is expanded in a Taylor series. Critical points can be classified according to their order, degeneracy or structural stability. The order of a critical point refers to the degree of the leading non zero term in the Taylor series. A critical point is non degenerate if this leading term is sufficient to give a qualitative description of the flow lines in the neighbourhood. A critical point is structurally stable if the flow lines in the neighbourhood do not change drastically when there is a small perturbation of the electromagnetic field. It is found that lowest order critical points, i.e., elementary center point and elementary saddle point, are the only structurally stable critical points. These critical points are always non degenerate. All degenerate and non elementary critical points are found to be structurally unstable. A formula for the index of rotation of the S field at a critical point is derived. The behaviour of the electric or the magnetic field component which lies in the x-y plane is also studied. It is shown that structurally unstable configurations of flow lines change into structurally stable configurations under small perturbations in such a way that the index of rotation is conserved. The statements made above in connection with the behaviour of flow lines and structural stability are illustrated with the help of examples involving linearly polarized system of interfering plane and/or cylindrical waves.
\r\n\r\nThe flow lines of the S field in the vicinity of a perfectly conducting surface are studied. It is found that in structurally stable situations these lines are either parallel to the surface or they form critical points of half saddle type on this surface. Two types of problems involving flow lines and conducting surfaces are identified. The interior problem deals with the situations where all the flow lines are inside a region bounded by a perfect conductor. In the exterior problems all the flow lines are outside a region bounded by a perfectly conducting surface. Conclusions regarding the existence of critical points and the behaviour of flow lines are drawn in the two above mentioned problems. These conclusions are verified by computation of flow lines in a few well known problems of scattering and diffraction.
\r\n\r\nFinally the critical points of three dimensional Poynting vector fields are considered. A complete classification of these critical points requires further study at this time. In this thesis only structurally stable critical points are classified for these S fields. An example demonstrating the existence of such critical points is given.
", "doi": "10.7907/gj18-eq28", "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:1630", "collection": "thesis", "collection_id": "1630", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05052006-103604", "primary_object_url": { "basename": "Rakuljic_ga_1987.pdf", "content": "final", "filesize": 3875425, "license": "other", "mime_type": "application/pdf", "url": "/1630/1/Rakuljic_ga_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Photorefractive Properties and Applications of Barium Titanate and Tungsten Bronze Ferroelectrics", "author": [ { "family_name": "Rakuljic", "given_name": "George Anthony", "clpid": "Rakuljic-George-Anthony" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Beck", "given_name": "James L.", "clpid": "Beck-J-L" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Rossman", "given_name": "George Robert", "clpid": "Rossman-G-R" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis is an experimental and theoretical investigation of the photorefractive properties of barium titanate and tungsten bronze ferroelectrics, and applications thereof. In the first part, the physics of the photorefractive effect is presented. The band transport equations are solved for three cases that describe the photorefractive mechanism in a crystal with one photorefractive species and either one or two types of charge carriers, or in a crystal with two photorefractive species, but only one type of charge carrier.
\r\n\r\nIn the second part, the coupled wave theory of two-wave mixing in photorefractive crystals is reviewed. Effects of energy coupling between the two interacting beams are discussed along with experimental methods for determining the two-beam coupling coefficient and the photorefractive response time.
\r\n\r\nThe photorefractive crystals barium titanate, strontium barium niobate, and barium strontium potassium sodium niobate are described in the third part. A summary of their optical, physical and electrical properties is presented for use in subsequent sections of the thesis.
\r\n\r\nIn the fourth part, the photorefractive properties of these crystals are presented. Data from two-beam coupling experiments are used to obtain the two-beam coupling coefficients and the photorefractive response times of the crystals under a variety of experimental conditions. The band transport models are then applied to these results.
\r\n\r\nFigures of merit are defined in the fifth part that are then used in a comparison of several photorefractive materials, including the barium titanate, the strontium barium niobate, and the barium strontium potassium sodium niobate crystals. Both ferroelectric and non-ferroelectric materials are considered.
\r\n\r\nIn the last part, applications using barium titanate and the tungsten bronze ferroelectrics are described. By using the self-focusing properties of barium titanate and strontium barium niobate, the compensation of nonlinear optical distortions with phase conjugation is demonstrated. A passive phase conjugator that relies on no external mirrors and uses strontium barium niobate as the nonlinear medium is also described. Finally, a thresholding passive phase conjugate mirror is then presented along with several devices that can perform mathematical operations on images such as subtraction and differentiation.
", "doi": "10.7907/8w0w-ea37", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1638", "collection": "thesis", "collection_id": "1638", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05052006-155412", "type": "thesis", "title": "Time and Space Integrating Acousto-Optic Signal Processing", "author": [ { "family_name": "Wagner", "given_name": "Kelvin H.", "clpid": "Wagner-Kelvin-H" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Masson", "given_name": "Colin R.", "clpid": "Masson-Colin-R" }, { "family_name": "Lesh", "given_name": "James R.", "clpid": "Lesh-James-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "One dimensional acousto-optic signal processing techniques are examined from the systems and functional viewpoint, and are then used as building blocks to synthesize multidimensional time and space integrating architectures. Time and space integrating signal processing systems are capable of performing 2-dimensional linear transformations upon images or matrices, by sequentially entering rows of the image with a travelling wave acousto-optic Bragg cell. The travelling rows are frozen by a pulsed laser diode, and the stationary diffracted fields are spatially processed by an optical system. The successively transformed rows are sequentially multiplied by a time varying reference wavefront, and accumulated on a time integrating CCD detector array to complete the two dimensional processing. Long 1-dimensional signals can also be linearly transformed by a time and space integrating system, by using a similar strategy upon a folded, or rastered, version of the high time bandwidth product signal. Small pieces of the long signal are slid into the system with an acousto-optic devices, and are spatially transformed over the device aperture. Then, successively transformed portions of the long signal are multiplied by a reference, and appropriately delayed and accumulated on a 2-D CCD in order to perform multichannel time integrations in the orthogonal dimension. The desired high time bandwidth one dimensional linear transformation is represented in the folded coordinate space of the 2-dimensional output detector.
\r\n\r\nThe operational characteristics of the principal active devices used in these time and space integrating systems are examined from the viewpoint of the system architect. The effects of the devices on the overall system operation are discussed, and device designs intended for application in a time and space integrating system operating environment are proposed.
\r\n\r\nThe final chapter is a detailed theoretical and experimental investigation into the particular operating characteristics of systems designed to perform a folded spectrum analysis of very high time bandwidth signals. This spectrum analysis problem has a shift variant transformation kernel, which can be broken down into a succession of smaller temporal and spatial sub transformations. The 1-dimensional space integrating spectrum analysis operation performed by a lens is used to produce a coarse spectral channelization of the input signal, displayed as a one dimensional spatial profile. Each resolvable spectral channel is fine frequency analyzed by temporal integration, producing a resulting intensity variation of each channel in the orthogonal direction, thereby forming a folded representation of the desired high time bandwidth spectrum analysis. The information which is needed to perform the fine frequency analysis is carried on the optical phase, so interferometric techniques are employed in order to detect the phase and transform it to an optical intensity modulation. Various bias terms are produced on the detector by the interferometric detection operation, and techniques for removing the unwanted bias are investigated. These include spatial carrier encoding of the interferometric terms combined with bandpass filtering, and direct bias subtraction techniques.
", "doi": "10.7907/4WH0-H941", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:2583", "collection": "thesis", "collection_id": "2583", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06142006-094757", "primary_object_url": { "basename": "Hong_jh_1987.pdf", "content": "final", "filesize": 13705251, "license": "other", "mime_type": "application/pdf", "url": "/2583/1/Hong_jh_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optical Computing for Adaptive Signal Processing and Associative Memories", "author": [ { "family_name": "Hong", "given_name": "John Hyunchul", "clpid": "Hong-John-Hyunchul" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Sideris", "given_name": "Athanasios", "clpid": "Sideris-A" }, { "family_name": "Koch", "given_name": "Christof", "orcid": "0000-0001-6482-8067", "clpid": "Koch-C" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical techniques for performing two computing tasks are investigated. First, acousto-optical systems that implement adaptive filtering structures are presented for operation in environments that are not well characterized a priori or are time-varying. Theoretical analyses along with experimental confirmations are given to identify the important system parameters that affect the performance. Extensions of the systems to the multidimensional domain of phased array signal processing are discussed as well as novel implementations that use photorefractive crystals as time-integrating elements.
\r\n\r\nAlso investigated are various associative memory models. An acousto-optic implementation of the so-called Hopfield model is presented. The system's storage capacity and attraction radius are characterized experimentally and are shown to agree with computer simulations. Secondly, an upper bound is derived for the storage capacity of holographic associative memories that use planar holograms. It is shown that if the space bandwidth product of the hologram is N2, then the holographic memory can store at most N2/N3 associations, where N3 is the number of pixels in each output item. Finally, associative memories whose performance is invariant with respect to shifts in the input pattern position are considered. It is shown that nonlinear interconnections are required to achieve shift invariant operation, and optical implementations are discussed.
\r\n", "doi": "10.7907/3vpt-fn50", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:824", "collection": "thesis", "collection_id": "824", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03012008-132010", "primary_object_url": { "basename": "Bonnefoi_ar_1987.pdf", "content": "final", "filesize": 11018493, "license": "other", "mime_type": "application/pdf", "url": "/824/1/Bonnefoi_ar_1987.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Electronic Properties and Device Applications of GaAs/Al\u2093Ga\u2081\u208b\u2093As Quantum Barrier and Quantum Well Heterostructures", "author": [ { "family_name": "Bonnefoi", "given_name": "Alice Ren\u00e9e", "clpid": "Bonnefoi-Alice-Ren\u00e9e" } ], "thesis_advisor": [ { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Bellan", "given_name": "Paul Murray", "clpid": "Bellan-P-M" } ], "thesis_committee": [ { "family_name": "McGill", "given_name": "Thomas C.", "clpid": "McGill-T-C" }, { "family_name": "Johnson", "given_name": "William Lewis", "clpid": "Johnson-W-L" }, { "family_name": "Tombrello", "given_name": "Thomas A.", "clpid": "Tombrello-T-A" }, { "family_name": "Corngold", "given_name": "Noel Robert", "clpid": "Corngold-N-R" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Bellan", "given_name": "Paul Murray", "clpid": "Bellan-P-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents an experimental and theoretical study of some of the electronic properties and device applications of GaAs/AlxGa1-xAs single and double barrier tunnel structures. In Chapter 2, energy band diagrams are calculated for heterostuctures in which tunneling occurs between two degenerately doped electrodes separated by a single quantum barrier. When a bias voltage is applied to a structure, the energy band profile gives the voltage drop distribution in the cladding layers as well as in the barrier. This distribution may differ significantly from that based on the commonly made assumption that the entire applied voltage drops linearly across the barrier layer. It is shown that band bending effects become more important for larger applied voltages, thicker barriers, smaller electrode doping densities and larger barrier doping concentrations. Energy band diagrams are found to be useful for calculating tunneling currents and determining what the dominant low temperature current transport mechanisms occurring in these structures are. In some cases, they reveal that these mechanisms are different from those predicted when band bending is neglected.
\r\n\r\nIn Chapter 3, elastic and inelastic tunneling processes are investigated in GaAs-AlAs-GaAs single barrier heterostructures grown on [100]-oriented substrates. The GaAs electrodes are degenerately doped n-type with Se, and the AlAs quantum barriers are doped either p-type with Mg or n-type with Se. In p-type barrier structures, low temperature current transport is found to be dominated by elastic and inelastic electron tunneling through the AlAs band gap at the \u0393-point and at the X-point. Anomalous zero-bias conductances obtained from several of the samples are also discussed. A theoretical model, which treats trap levels in the AlAs barrier as intermediate states for two-step tunneling processes shows that impurity-assisted tunneling becomes more important as the tunnel barrier is made thicker. In heterostructures in which the n-type barrier layers are thick enough and/or sufficiently doped, the AlAs conduction band at the X-point is not totally depleted of electrons. The dominant low temperature current transport mechanism is then tunneling through two reduced AlAs X-point barriers separated by a bulk region of AlAs. When the n-type AlAs barrier layer is sufficiently thin, the AlAs conduction band remains fully depleted of carriers. As a result, electrons tunnel through the AlAs band gap at the X-point and/or at the \u0393-point in a one-step process. In these structures, it is found that plasmons located near the GaAs/AlAs interfaces interact with GaAs and AlAs longitudinal optical (LO) phonons when the doping density in the n-type GaAs electrodes is such that the plasma frequency becomes comparable to the LO phonon frequencies.
\r\n\r\nChapter 4 presents a study of resonant tunneling in GaAs/AlxGa1-xAs double barrier heterostructures grown epitaxially in the [100]-direction. In these structures, electrons tunnel through two AlxGa1-xAs quantum barriers separated by a thin GaAs layer forming a quantum well. The resonant energy levels in the GaAs well which produce negative differential resistances in the experimental I-V characteristics are identified by calculating the energy band diagrams of the structures. In samples having pure AlAs barrier layers, tunneling via resonant states confined in the well by the AlAs \u0393-point potential energy barriers is often inconsistent with experimental results. However, the experimental data can usually be explained by tunneling via quasi-stationary levels confined in the well by the AlAs X-point potential energy barriers as well as the AlAs \u0393-point barriers. The relative contributions of tunneling via resonant \u0393- and X-states in the well are found to depend upon the samples studied and sometimes upon the sign of the applied bias. Resonant tunneling is also investigated in double barrier heterostructures in which a low doped GaAs buffer layer is grown before the first AlxGa1-xAs barrier. As a result of this structural asymmetry, the peaks in current corresponding to a given resonant state in the quantum well may be observed in the experimental I-V characteristics at very different applied voltages in reverse bias than in forward bias.
\r\n\r\nIn Chapter 5, we propose and analyze two types of three-terminal devices based upon resonant tunneling through quantum well and quantum barrier heterostructures. The first type includes two configurations in which a base voltage controls the emitter-collector tunneling current by shifting the resonances in a quantum well. In the proposed devices, the relative positions of the base and collector are interchanged with respect to the conventional emitter-base-collector sequence as a means for obtaining negligible base currents and large current transfer ratios. The second type of three-terminal devices includes three configurations in which the current through a double barrier structure is modulated by a Schottky barrier gate placed along the path of the electrons. These devices feature, in their output current-voltage (ID-VD) curves, negative differential resistances controlled by a gate voltage.
\r\n\r\nChapter 6 presents a growth uniformity study performed on several of the heterostructures discussed in the thesis. First, the reproducibility and uniformity of the electrical characteristics of GaAs/AlAs tunnel structures are used to show that the doping concentrations and layer thicknesses are uniform across the samples under test. Secondly, discrete fluctuations in layer thicknesses are discussed in GaAs/Al0.35Ga0.65As double barrier heterostructures. These fluctuations are manifested by non-uniform experimental results and by sequences of negative differential resistances in the I-V characteristics of many devices.
", "doi": "10.7907/c4q6-2176", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:808", "collection": "thesis", "collection_id": "808", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02282008-090141", "primary_object_url": { "basename": "Bassiri_s_1987.pdf", "content": "final", "filesize": 1767433, "license": "other", "mime_type": "application/pdf", "url": "/808/1/Bassiri_s_1987.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Electromagnetic Wave Propagation and Radiation in Chiral Media", "author": [ { "family_name": "Bassiri", "given_name": "Sassan", "clpid": "Bassiri-Sassan" } ], "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": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Elachi", "given_name": "Charles", "clpid": "Elachi-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Propagation and radiation of electromagnetic waves in a lossless, reciprocal, chiral medium is studied in this thesis. Such a medium is described electromagnetically by the constitutive relations D = \u03b5E + i\u03b3B and H = i\u03b3E + (1/\u00b5)B. The constants \u03b5, \u00b5, \u03b3 are real and have values that are fixed by the size, shape, and the spatial distribution of the elements that collectively compose the medium. The plane wave propagation in an unbounded chiral medium is considered. The propagation constants are obtained and the polarization properties of electromagnetic waves in such a medium are discussed in detail. The problem of reflection from, and transmission through a semi-infinite chiral medium is solved by obtaining the Fresnel equations. The conditions for the total internal reflection of the incident wave from the interface, and the existance of the Brewster angle are obtained. The effects of the chirality on the polarization and intensity of the reflected wave from the chiral half-space are discussed and illustrated by employing the Stokes parameters. The propagation of electromagnetic waves through an infinite slab of chiral medium is formulated for oblique incidence and solved analytically for the case of normal incidence. The radiation emitted by an oscillating dipole in an unbounded, lossless, chiral medium is calculated. From the constitutive relations and from the time-harmonic Maxwell equations \u2207 x E = i\u03c9B and \u2207 x H = J - i\u03c9D, it is seen that the wave equation for such a medium is given by \u2207 x \u2207 x E - \u03c92\u00b5\u03b5E - 2\u03c9\u00b5\u03b3\u2207 x E = i\u03c9\u00b5J where the source term J is the current density of the oscillating dipole and where E is the electric vector of the radiated field. The desired solution of this wave equation is found by the dyadic Green's function method, that is, by first constructing the dyadic Green's function \u0393 and then evaluating the expression E = i\u03c9\u00b5\u222b\u0393(r,r')\u2022J(r')dV'. The dyadic Green's function \u0393 and the components of the radiated electric field E are obtained in closed form. The components of the radiated B, D, and H fields can be derived from knowledge of E by using the Maxwell equation B = (1/i\u03c9)\u2207 x E and the constitutive relations. The wave impedance of the medium and the radiation resistance of the dipole are also obtained. The effects of the chiral medium on the polarization and intensity of the dipole radiation are discussed.
", "doi": "10.7907/RFST-5K65", "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:883", "collection": "thesis", "collection_id": "883", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03052008-095021", "type": "thesis", "title": "Linear Maps with Point Rules: Applications to Pattern Classification and Associative Memory", "author": [ { "family_name": "Venkatesh", "given_name": "Santosh Subramanyam", "clpid": "Venkatesh-Santosh-Subramanyam" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Franklin", "given_name": "Joel N.", "clpid": "Franklin-J-N" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Generalisations of linear discriminant functions are introduced to tackle problems in pattern classification, and associative memory. The concept of a point rule is defined, and compositions of global linear maps with point rules are incorporated in two distinct structural forms\u2014feedforward and feedback\u2014to increase classification flexibility at low increased complexity. Three performance measures are utilised, and measures of consistency established.
\r\n\r\nFeedforward pattern classification systems based on multi-channel machines are introduced. The concept of independent channels is defined and used to generate independent features. The statistics of multi-channel classifiers are characterised, and specific applications of these structures are considered. It is demonstrated that image classification invariant to image rotation and shift is possible using multi-channel machines incorporating a square-law point rule. The general form of rotation invariant classifier is obtained. The existence of optimal solutions is demonstrated, and good sub-optimal systems are introduced, and characterised. Threshold point rules are utilised to generate a class of low-cost binary filters which yield excellent classification performance. Performance degradation is characterised as a function of statistical side-lobe fluctuations, finite system space-bandwidth, and noise.
\r\n\r\nSimplified neural network models are considered as feedback systems utilising a linear map and a threshold point rule. The efficacy of these models is determined for the associative storage and recall of memories. A precise definition of the associative storage capacity of these structures is provided. The capacity of these networks under various algorithms is rigourously derived, and optimal algorithms proposed. The ultimate storage capacity of neural networks is rigourously characterised. Extensions are considered incorporating higher-order networks yielding considerable increases in capacity.
", "doi": "10.7907/1YSB-Q028", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:2734", "collection": "thesis", "collection_id": "2734", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06262006-133025", "primary_object_url": { "basename": "VanZyl_jj_1986.pdf", "content": "final", "filesize": 7972149, "license": "other", "mime_type": "application/pdf", "url": "/2734/1/VanZyl_jj_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "On the Importance of Polarization in Radar Scattering Problems", "author": [ { "family_name": "van Zyl", "given_name": "Jakob Johannes", "clpid": "van-Zyl-Jakob-Johannes" } ], "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": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Elachi", "given_name": "Charles", "orcid": "009-0002-2156-967X", "clpid": "Elachi-C" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this thesis, the importance of polarization in radar scattering problems is investigated. The different matrix characterizations of scatterers are discussed in detail. The problem of finding the polarizations which would yield an optimum amount of power received from the scatterer is solved for the most general case. This shows that for certain classes of scatterers six optimum polarizations exist. The concept of a polarization spectrum to characterize a scatterer is introduced. The usefulness of these spectrums is illustrated when results, using measured multipolarization synthetic aperture radar data, are discussed. Another useful parameter, the coefficient of variation, is introduced. Measured results show that this parameter may be used to form an idea of the scale over which the scattering properties of the scene being imaged vary. The problem of finding the effective scattering operator of a slab filled with different scatterers is formulated. Detailed expressions are given for the effective single scattering operators. This formulation is illustrated by calculating the effective single scattering operators for models of different types of vegetation.
", "doi": "10.7907/QRD0-YE09", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:11461", "collection": "thesis", "collection_id": "11461", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04152019-101001395", "type": "thesis", "title": "Optical Interactions in a Dielectric Material with Multiple Perturbations", "author": [ { "family_name": "Lee", "given_name": "Hyuk", "clpid": "Lee-Hyuk" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "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" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The interaction of light propagating through a dielectric material with multiple perturbations is investigated.
\r\n\r\nA general coupled mode theory of two gratings is presented. The acousto-electro-optic effect is introduced as an example of an indirect interaction due to the acousto-optic and electro-optic effects. The acousto-electro-optic effect is analyzed using the general theory and is demonstrated experimentally. The application of this effect to light modulation and deflection is discussed in detail. Also a correlator that is based on the photorefractive acousto-electrooptic effect is demonstrated and analyzed theoretically.
", "doi": "10.7907/ek2w-4557", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:1020", "collection": "thesis", "collection_id": "1020", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03192008-121641", "primary_object_url": { "basename": "Haney_mw_1986.pdf", "content": "final", "filesize": 15585280, "license": "other", "mime_type": "application/pdf", "url": "/1020/1/Haney_mw_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Acousto-Optical Time-and-Space Integrating Processors for Real-Time Synthetic Aperture Radar Imaging", "author": [ { "family_name": "Haney", "given_name": "Michael William", "orcid": "0009-0001-8071-5561", "clpid": "Haney-Michael-William" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Elachi", "given_name": "Charles", "orcid": "009-0002-2156-967X", "clpid": "Elachi-C" }, { "family_name": "Masson", "given_name": "Colin R.", "clpid": "Masson-Colin-R" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Acousto-optical processors for Synthetic Aperture Radar (SAR) imaging are presented. The new processors produce images at real-time rates by combining the operations of data collection, storage, and processing into a compact time-and-space integrating (TSI) architecture. In the TSI approach the 2-D SAR imaging problem is decomposed into a cascade of 2 distinct operations: a 1-D spatial integration of light for range compression, and a 1-D temporal integration of light for azimuth compression. These two operations are coupled via a common path interferometric scheme that is insensitive to mechanical vibrations.
\r\n\r\nThe results of an experimental characterization of the TSI approach, with simulated point scatterer radar echoes, are reported. The performance issues of interferometric bias removal, dynamic range, and resolution are addressed. The architecture is generalized to correct for range migration and the results of a range walk compensation experiment are presented. A programmable version of the TSI architecture, in which the fixed azimuth reference mask is replaced by an acousto-optic light modulator, is described. The application of the programmable architecture to both strip-map and spot-light mode SAR is analyzed and experimentally verified.
", "doi": "10.7907/64T4-7N83", "publication_date": "1986", "thesis_type": "phd", "thesis_year": "1986" }, { "id": "thesis:957", "collection": "thesis", "collection_id": "957", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03142008-142149", "primary_object_url": { "basename": "Papantoniuo_da_1986.pdf", "content": "final", "filesize": 11067704, "license": "other", "mime_type": "application/pdf", "url": "/957/1/Papantoniuo_da_1986.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Observations in Turbulent Buoyant Jets by Use of Laser-Induced Fluorescence", "author": [ { "family_name": "Papantoniou", "given_name": "Dimitris Antony", "clpid": "Papantoniou-Dimitris-Antony" } ], "thesis_advisor": [ { "family_name": "List", "given_name": "E. John", "clpid": "List-E-J" } ], "thesis_committee": [ { "family_name": "List", "given_name": "E. John", "clpid": "List-E-J" }, { "family_name": "Sabersky", "given_name": "Rolf H.", "clpid": "Sabersky-R-H" }, { "family_name": "Coles", "given_name": "Donald Earl", "clpid": "Coles-D-E" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Cohen", "given_name": "Donald S.", "clpid": "Cohen-D-S" } ], "local_group": [ { "literal": "GALCIT" }, { "literal": "div_eng" } ], "abstract": "The entrainment mechanism and mixing process are investigated in the far field of a liquid phase buoyant jet issuing into an unconfined, quiescent medium, by an experimental technique based on laser-induced fluorescence (LIF). Visualization experiments show the existence of a large scale organization in the far field, with structures spanning the radial extent of the conical flow region. Quantitative, high-resolution measurements of scalar concentration were performed along the radial direction in the far field region. For each data set, a large number of successive instantaneous concentration profiles were obtained by combining LIF techniques with linear photodiode array imaging and high speed data acquisition. The measurements revealed that the instantaneous profile bears no resemblance to the time-averaged profile. The flow interior is characterized by large spatial gradients of concentration, associated with interfaces between mixed jet fluid and fresh, entrained ambient fluid transported to regions deep into the flow. This is inconsistent with the description of transport by gradient diffusion concepts. The probability of finding unmixed ambient fluid and the concentration variance are greatly increased under the action of buoyancy. At any axial location, the arrival of a structure front is marked by a spatially coherent (along the radial direction) increase in the local concentration level. It is found that, within the structure, values of the concentration are generally decreasing in the upstream direction; substantial uniformity within the mixed fluid portion is observed along the radial direction. In the conical flow field of the momentum jet, a central region (in fixed spatial coordinates) may be identified within which the local mixed fluid composition is relatively uniform. This is not the case for the buoyancy driven plume, due to a greater variance in the position of the large structure and the high value of the intermittency. It is suggested that fluid is entrained by vortical motions mainly from the back and side regions of the large structure. Flow visualization reveals vorticity in the axial direction which enhances the mixing process; this vorticity appears stronger in the buoyancy driven flow. The results of these experiments are interpreted through a simple conceptual model of entrainment and mixing that encompasses the observed large scale organization of the buoyant jet flow.
", "doi": "10.7907/SX4D-3555", "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: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: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: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: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: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:297", "collection": "thesis", "collection_id": "297", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-01232007-143259", "primary_object_url": { "basename": "Warne_l_1984.pdf", "content": "final", "filesize": 3394777, "license": "other", "mime_type": "application/pdf", "url": "/297/1/Warne_l_1984.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Electromagnetic Radiation and Scattering in a Plasma with an Azimuthal Biasing Field", "author": [ { "family_name": "Warne", "given_name": "Larry Kevin", "clpid": "Warne-Larry-Kevin" } ], "thesis_advisor": [ { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" } ], "thesis_committee": [ { "family_name": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "clpid": "Psaltis-D" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Kath", "given_name": "William L.", "clpid": "Kath-William-L" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The problem of radiation from an electric line source in a homogeneous, cold, incompressible electron plasma is considered when a large static current is superposed. The static axial current gives rise to a magnetostatic biasing field which is oriented in the azimuthal direction and varies with radial distance. When the driving frequency is greater than the plasma frequency, and the medium is assumed to be unbounded, the presence of the static current reduces the amount of radiation. On the other hand, if the driving frequency is less than the plasma frequency and the medium is assumed to be bounded, the amount of radiation is increased.
\r\n\r\nThe problem of scattering from an axial current in a plasma is also considered. The medium in this problem is taken to be a bounded column of plasma containing a radially distributed axial current. At normal incidence the scattered wave contains a cross polarized field component due to the gyrotropic nature of the column. The scattered cross polarized component vanishes in the incident direction as well as in the backward direction. This null is explained by considering the effect of Faraday rotation on various rays traversing the column. Solutions to the scattering problem when the axial current density varies inversely with radial distance are considered in some detail. This case is labeled \"homogeneous\" since the dielectric tensor does not vary with radial distance and the resulting field equations are thus simplified. The field behavior in the vicinity of the origin is also considered in detail since phenomena similar to those encountered in wedge type media (unbounded fields) occur.
", "doi": "10.7907/tja8-zp12", "publication_date": "1984", "thesis_type": "phd", "thesis_year": "1984" }, { "id": "thesis:1786", "collection": "thesis", "collection_id": "1786", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05142003-111719", "type": "thesis", "title": "Complexity of Information Extraction", "author": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser Said", "clpid": "Abu-Mostafa-Yaser-Said" } ], "thesis_advisor": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" } ], "thesis_committee": [ { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Kechris", "given_name": "Alexander S.", "orcid": "0000-0002-2226-0423", "clpid": "Kechris-A-S" }, { "family_name": "McEliece", "given_name": "Robert J.", "clpid": "McEliece-R-J" }, { "family_name": "Mead", "given_name": "Carver", "orcid": "0000-0003-4051-0462", "clpid": "Mead-C-A" }, { "family_name": "Posner", "given_name": "Edward C.", "clpid": "Posner-E-C" }, { "family_name": "Ryser", "given_name": "Herbert J.", "clpid": "Ryser-H-J" }, { "family_name": "Wilson", "given_name": "Richard M.", "clpid": "Wilson-R-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes a mathematical theory that interrelates the basic concepts of complexity, cost, information and reliability. The accessibility of information, as opposed to its availability, is characterized. Universal bounds for complexity distribution, implementation cost and decision reliability are estimated. These bounds give rise to a methodology for any consistent definition of a complexity measure. The basic notions of pattern recognition and information theory are directly related to computational complexity.
", "doi": "10.7907/FVKM-7J60", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3355", "collection": "thesis", "collection_id": "3355", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-083609", "primary_object_url": { "basename": "Harder_cs_1983.pdf", "content": "final", "filesize": 11181635, "license": "other", "mime_type": "application/pdf", "url": "/3355/1/Harder_cs_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Bistability, High Speed Modulation, Noise and Pulsations in GaAlAs Semiconductor Lasers", "author": [ { "family_name": "Harder", "given_name": "Christoph S.", "clpid": "Harder-Christoph-S" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Peck", "given_name": "Charles W.", "clpid": "Peck-C-W" }, { "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": "McCaldin", "given_name": "James Oeland", "clpid": "McCaldin-J-O" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis describes seven different subjects relevant to semiconductor laser diodes which fall in the following three categories: Bistability and pulsations, high speed modulation and noise.
\r\n\r\nBistable semiconductor lasers based on inhomogeneous current injection, achieved with a split contact scheme, were proposed around 20 years ago. However, actual devices showed no or only a small hysteresis and they were in addition beset by pulsations for reasons not well understood at the time. In this thesis we show that lasers with an optimized design can display bistability with a giant hysteresis. Crucial to the understanding of the bistable laser is a negative differential resistance across the absorber section, reminiscent of a tunnel diode characteristic. Depending on the electrical biasing circuit this negative differential resistance leads to bistability or light-jumps and self-pulsations. A simple model based on the conventional rate equations explains the observed behavior. Investigation of the switching dynamics of this optoelectronic device reveals a delay time which is critically dependent on the trigger pulse amplitude and which is typically in the order of a few nanoseconds at a power-delay product of 100pJ. We also investigate the characteristic of this laser coupled to an external optical cavity and we demonstrate that this bistable laser can be used as a self-coupled stylus for optical disk readout. Under a different biasing condition this laser coupled to an external optical cavity can be used to generate ultrashort optical pulses through passive mode locking. Unlike previous mode locking techniques, the method presented here does not rely on absorption introduced by damaging the crystal and is consequently much more reliable.
\r\n\r\nThe high speed modulation behavior of semiconductor lasers is investigated theoretically and experimentally. In this thesis we derive the fundamental limits of injection lasers for pulse modulation and small signal modulation. We place emphasis on developing laser structures optimized for high frequency modulation and experiments on such structures show that they can be modulated at frequencies up to 8GHz. At these frequencies the parasitic elements can no longer be neglected and they are included in the analysis.
\r\n\r\nThe noise equivalent circuit of a semiconductor laser diode is derived from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise and frequency modulation characteristics of a laser diode combined with electronic components. The field spectrum of injection lasers is observed also experimentally. It is a unique feature of injection lasers that their linewidth is increased through a strong amplitude phase coupling by the factor (1 + \u03b12) where \u03b1 is the linewidth enhancement factor. A model is developed which shows that the same factor \u03b1 enters in the small signal modulation characteristics and a careful measurement of the small signal amplitude and phase modulation at high frequencies enables us to obtain this important factor \u03b1 for the first time by a direct measurement.
", "doi": "10.7907/jxwz-e844", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3360", "collection": "thesis", "collection_id": "3360", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09062006-131347", "type": "thesis", "title": "III-V Semiconductor Lasers and Detectors", "author": [ { "family_name": "Chiu", "given_name": "Liew-Chuang", "clpid": "Chiu-Liew-Chuang" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Nicolet", "given_name": "Marc-Aurele", "clpid": "Nicolet-M-A" }, { "family_name": "Margalit", "given_name": "Shlomo", "clpid": "Margalit-Shlomo" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Whaling", "given_name": "Ward", "clpid": "Whaling-W" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The subjects of this thesis can be divided into two main categories: III-V semiconductor lasers and detectors. The first two chapters are concerned with the InGaAsP/InP laser diodes. The final two chapters are related to fundamental problems in the avalanche photodiodes and the new class of quantum well infrared detectors.
\r\n\r\nThe kinetics of the mass transport phenomenon in InP is studied experimentally. Application of this technique to laser fabrication has resulted in very low threshold terrace mesa lasers.
\r\n\r\nThe continuing problem of the excess temperature sensitivity of InGaAsP lasers and light emitting diodes is studied in detail. Non-radiative Auger recombination and electron leakage are found to be important factors affecting the temperature sensitivities of these devices.
\r\n\r\nImpact ionization in the GaAlSb system is investigated. The resonant nature of the enhanced impact ionization of holes is discussed. Further enhancement is predicted to be possible in quantum well structures.
\r\n\r\nThe new class of quantum well infrared detectors is described. Theoretical considerations on absorption coefficients and other parameters essential to device design and performance are discussed.
", "doi": "10.7907/ttgs-8a70", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:3536", "collection": "thesis", "collection_id": "3536", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09142006-111227", "type": "thesis", "title": "Investigations of Near-Zone Doppler Effects", "author": [ { "family_name": "Prouty", "given_name": "Dale Austen", "clpid": "Prouty-Dale-Austen" } ], "thesis_advisor": [ { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" } ], "thesis_committee": [ { "family_name": "Wilts", "given_name": "Charles Harold", "clpid": "Wilts-C-H" }, { "family_name": "Papas", "given_name": "Charles Herach", "clpid": "Papas-C-H" }, { "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" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Far away from an electromagnetic source the normal Doppler shifts in frequency occur \u2013 a red shift for receding and a blue shift for approaching. As indicated by previous work with an infinitesimal dipole, different frequency shifts occur when the source and observer move closer together, into the near-zone. These \"near-zone Doppler effects\" are investigated for general sources and subsequently two specific examples are presented.
\r\n\r\nThe general results show that near-zone shifts are similar to far-zone shifts, but the local phase velocity must be used, i.e. \u03c9' \u2243 \u03c9(1 \u00b1 (v/vph)). In the far zone the phase velocity is the speed of light; in the near zone it differs. Fundamentally, the distance between surfaces of constant phase in the near zone is changed. The surfaces of constant phase for the waves are no longer spherical, but more ellipsoidal or spheroidal, so that a moving observer sees a different frequency shift.
\r\n\r\nTwo specific examples are presented to indicate the actual magnitude of near-zone effects. The examples include a prolate spheroidal antenna and a circular aperture.
\r\n\r\nOnce the magnitude of the effects is determined, the measurability of near-zone Doppler effects is discussed. The investigation concentrates on Fresnel zone effects due to the measurement problem.
\r\n\r\nFinally, it is shown that for an electrically large wire antenna (the spheroidal example) near-zone Doppler effects are measurable.
", "doi": "10.7907/vfzj-7d74", "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: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: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:3533", "collection": "thesis", "collection_id": "3533", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09142006-080653", "type": "thesis", "title": "On the Radiation Patterns of Interfacial Antennas", "author": [ { "family_name": "Engheta", "given_name": "Nader", "orcid": "0000-0003-3219-9520", "clpid": "Engheta-Nader" } ], "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": "Martel", "given_name": "Hardy Cross", "clpid": "Martel-H-C" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Elachi", "given_name": "Charles", "orcid": "009-0002-2156-967X", "clpid": "Elachi-C" }, { "family_name": "Kavanagh", "given_name": "Ralph William", "clpid": "Kavanagh-R-W" } ], "local_group": [ { "literal": "Caltech Distinguished Alumni Award" }, { "literal": "div_eng" } ], "abstract": "The radiation pattern of an interfacial radiating source is obtained for the case where the source is an infinitely long line source lying along the plane interface of two dielectric half-spaces; for the case where the source is an infinitesimal electric dipole vertically located on the interface; and for the case where the dipole is lying horizontally along the interface. For all the three cases, it is found that the radiation pattern at the interface has a null (interface extinction). For the infinitely long line source, it is obtained that the pattern in the upper half-space, whose index of refraction is taken to be less than that of the lower half-space, has a single lobe with a maximum normal to the interface, and that the pattern in the lower half-space (subsurface region) has two maxima straddling symmetrically a minimum. Interpretation of these results in terms of ray optics, Oseen's extinction theorem, and the Cerenkov effect are given. For the vertical dipole, it is found that the radiation pattern along the dipole axis has a null. For the horizontal dipole, it is obtained that the pattern in the upper half-space has a single lobe whose maximum is normal to the interface; that in the lower half-space, in the plane normal to the interface and containing the dipole, the pattern has three lobes; whereas in the plane normal to the interface and normally bisecting the dipole, the pattern has two maxima located symmetrically about a minimum. Interpretation of these results in terms of the Cerenkov effect is also given.
", "doi": "10.7907/y86x-2709", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "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" } ]