Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / Vita. / Includes bibliographies. / Ph.D.

Li Xin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 81-86). / Abstracts in English and Chinese. / COHERENT OPTICAL CODE DIVISION MULTIPLE ACCESS BASED ON SUPERSTRUCTURE FIBER BRAGG GRATING ENCODERS AND DECODERS --- p.1 / ACKNOWLEDGEMENT --- p.2 / ABSTRACT --- p.III / 摘要 --- p.V / CONTENTS --- p.VI / LIST OF FIGURES --- p.1 / Chapter CHAPTER 1 --- INTRODUCTION --- p.3 / Chapter 1.1 --- Overview of OCDMA --- p.3 / Chapter 1.2 --- Classification of OCDMA Schemes --- p.6 / Chapter 1.3 --- Introduction of Coherent OCDMA Schemes --- p.9 / Chapter 1.4 --- Introduction of superstructure Fiber Bragg Gratings and Other Encoding and Decoding Components --- p.10 / Chapter 1.5 --- Outline of the Thesis --- p.13 / Chapter CHAPTER 2 --- COUPLED MODE THEORY AND SUPERSTRUCTURE FIBER BRAGG GRATING SIMULATION MODEL --- p.16 / Chapter 2.1 --- Fiber Bragg Grating Model Based on Coupled Mode Theory --- p.16 / Chapter 2.1.1 --- Introduction of FBG and the Coupled Mode Theory --- p.16 / Chapter 2.1.2 --- FBG Model Based on CMT --- p.18 / Chapter 2.1.3 --- FBG Model When there are Phase Discontinuities Between Different Parts --- p.20 / Chapter 2.2 --- Properties of Fiber Bragg Gratings --- p.22 / Chapter 2.3 --- Simulation Model of superstructure Fiber Bragg Gratings --- p.27 / Chapter 2.4 --- Summary --- p.31 / Chapter CHAPTER 3 --- COHERENT OCDMA CODING SCHEME BASED ON THE SUPERSTRUCTURE FIBER BRAGG GRATING ENCODER/DECODER --- p.33 / Chapter 3.1 --- Introduction and Theoretical Derivation of the Coding Scheme --- p.33 / Chapter 3.1.1 --- Introduction of the Coding Scheme --- p.33 / Chapter 3.1.2 --- Derivation of SSFBG Encoder --- p.34 / Chapter 3.1.3 --- Encoding for the SSFBG --- p.39 / Chapter 3.2 --- Introduction of the Simulation Model and the Research on It …… --- p.44 / Chapter 3.3 --- Summary --- p.47 / Chapter CHAPTER 4 --- RESEARCH ON THE SIMULATED COHERENT OCDMA SYSTEM IN IDEAL CASE --- p.48 / Chapter 4.1 --- Introduction of the ideal case and factors that affect the system performance --- p.48 / Chapter 4.2 --- Effects by Refractive Index Modulation of the SSFBG Encoder --- p.49 / Chapter 4.3 --- Effects by Code Type --- p.54 / Chapter 4.4 --- Effect by the Code Length --- p.57 / Chapter 4.5 --- Summary --- p.60 / Chapter CHAPTER 5 --- RESEARCH ON THE SIMULATED COHERENT OCDMA SYSTEM IN PRACTICAL ENVIRONMENT --- p.62 / Chapter 5.1 --- Introduction --- p.62 / Chapter 5.2 --- Comparison of System Performance in Synchronous and Asynchronous Cases --- p.63 / Chapter 5.3 --- Discussion on the System Performance When Users are In Different Power Levels --- p.65 / Chapter 5.4 --- Analysis of Channel Noise In the Coherent OCDMA System --- p.68 / Chapter 5.5 --- Summary --- p.70 / Chapter CHAPTER 6 --- CONCLUSIONS AND FUTURE WORK --- p.72 / Chapter 6.1 --- Conclusions --- p.72 / Chapter 6.2 --- Future Work --- p.75 / APPENDIX A PROOF OF SSFBG THEORETICAL MODEL APPROXIMATION --- p.77 / "APPENDIX B RANDOM SEQUENCE, M-SEQUENCE AND WALSH SEQUENCE" --- p.80 / REFERENCES --- p.81

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / Microfiche copy available in Archives and Barker. / Includes bibliographical references. / by Steven James Hollowell. / M.S.

The concern of this thesis was to investigate the nonlinear dynamics inherent in oscillating waterfalls.

Abstract not available

For thesis abstract select View Thesis Title, Contents and Abstract

Thesis (Ph. D.)--Oregon State University, 1993. / Typescript (photocopy). Includes bibliographical references (leaves 102-110). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, December 2002. / Includes bibliographical references. Also available on the Internet.

Les micro-résonateurs à modes de galerie, qu'ils soient déclinés sous forme de disques, anneaux ou hippodromes, sont devenus les éléments constitutifs clés de nombreux composants photoniques de haute performance. Les réalisations exploitant les semiconducteurs III-V sont particulièrement attrayantes car elles ouvrent la possibilité d'intégrer conjointement des sections actives et passives et donc de diversifier les fonctionnalités sur une même puce photonique. Au niveau technologique, l'intégration verticale du résonateur au-dessus de ses guides d'accès permet de distribuer les fonctions actives et passives sur des plans distincts et de faciliter la réalisation des composants grâce à des procédés mieux maitrisés. Une technique de fabrication récemment introduite dans l'équipe et basée sur la filière AlGaAs/AlOx a ainsi permis de réaliser, à l'aide d'étapes simples, des micro-disques couplés verticalement à leur guide d'accès. Les performances de ces composants restent toutefois limitées en raison de leur architecture, complexifiée par les empilements multicouches qui les constituent.Les travaux de recherche menés au cours de cette thèse ont porté sur la faisabilité d'émettre un peigne de fréquences optiques à partir de ces résonateurs. Pour cela, les composants doivent être conçus de manière à présenter un facteur de qualité suffisamment élevé tout en maximisant la puissance circulant dans la cavité, afin de pouvoir déclencher les processus non-linéaires à la base de la génération du peigne. Pour un composant monomode transverse, la puissance intracavité est maximale lorsque le système opère en régime de couplage critique, c'est-à-dire lorsque les pertes internes à la cavité sont égales aux pertes externes (ou pertes par couplage). Nous avons donc développé un outil semi-analytique basé sur une expansion modale afin de réaliser une modélisation paramétrique large bande des performances des systèmes couplés verticalement, encore peu étudiés, tant au plan théorique que pratique. Notre modèle générique exploite la théorie des modes couplés (CMT) et les relations universelles régissant les propriétés spectrales des micro-résonateurs couplés. Nous l'avons étendu en étudiant l'influence spectrale de différents paramètres opto-géométriques sur la fonction de transfert de la cavité couplée et avons, en particulier, mis en évidence par une approche variationnelle, deux conditions théoriques permettant d'obtenir un régime critique achromatique lorsque la cavité et son guide d'accès sont désaccordés en phase. Ce modèle à d'abord été appliqué à la simulation de résonateurs en hippodromes exploitant la filière Si3N4/SiO2 car plusieurs études ont déjà démontré la génération de peignes avec cette plateforme technologique. Ces travaux ont abouti au dessin de structures désaccordées en phase et technologiquement réalisables dont la bande passante critique est augmentée d'un ordre de grandeur par rapport au cas plus répandu de guides accordés en phase. Nous avons ensuite initié une évaluation numérique de la génération de peignes de fréquences, basée sur la résolution itérative de l'équation de Schrödinger non-linéaire prenant en compte les variations des propriétés spectrales et dispersives de ces hippodromes. Le modèle générique a enfin été appliqué aux micro-disques AlGaAs/AlOx. Pour cela, nous avons introduit un critère permettant d'utiliser la CMT dans le cas de coupleurs asymétriques présentant une zone de séparation multicouche. Les résultats, en bon accord avec l'expérience, nous ont permis de mieux appréhender les limitations des dispositifs réalisés et de proposer de nouvelles structures pour en améliorer les performances. Le dessin d'une nouvelle structure AlGaAs/AlOx multicouche permettant d'améliorer les facteurs de qualité des résonateurs jusqu'à deux ordres de grandeurs a ainsi été proposé. La validation expérimentale des dessins proposés tant pour la filière Si3N4/SiO2 que AlGaAs/AlOx est en cours. / Whispering-gallery -mode micro-resonators, whether in the form of disks, rings or racetracks, have become the key building blocks of many high-performance photonic components. The embodiments exploiting the III-V semiconductors are particularly attractive for they open the possibility of integrating active and passive sections together and therefore diversify the functionalities on the same photonic chip. Furthermore, the vertical integration of the resonator above its access waveguide(s) makes it possible to distribute the active and passive functions on distinct planes and makes the realization of the components easier by using better-controlled methods. A fabrication technique recently introduced in the team and based on the AlGaAs / AlOx technological platform, allowed us to realize, by means of simple steps, vertically-coupled microdisks. The performance of these components, however, is limited due to their architecture, complicated by their constitutive multilayer stack. The research carried out during this PhD thesis focused on the feasibility of emitting an optical frequency comb from these resonators. For this purpose, the components must be designed so as to present a sufficiently high quality factor while maximizing the power circulating in the cavity in order to be able to trigger the non-linear processes required for the comb generation. For a transverse single-mode component, the intracavity power is maximal when the system operates in critical coupling regime, i.e .when the losses inside the cavity are equal to external losses (or coupling losses). As a first step, we have developed a semi-analytical tool based on a modal expansion in order to carry out a broadband parametric study of the performances of vertically coupled systems. Up to now, this coupling layout has indeed been little studied, both theoretically and practically. Our generic model, based on the coupled mode theory (CMT) and the universal relations governing the spectral properties of coupled micro-resonators, reveals two theoretical conditions for obtaining an achromatic critical-coupling regime when the cavity and its access waveguide are phase-mismatched. We first applied it to the simulation of single- mode racetrack resonators made of Si3N4 / SiO2 since several studies have already demonstrated comb generation using this technological platform. Our work resulted in the design of phase-mismatched and technologically feasible structures with critical-copuling bandwidths being increased by one order of magnitude compared to the reference case of phase- matched waveguides. We subsequently initiated a numerical evaluation of frequency comb generation, based on the iterative resolution of the non-linear Schrödinger equation taking into account the variations of the spectral and dispersive properties of these racetracks. The generic model has finally been applied to AlGaAs / AlOx microdisks. For this purpose, we have introduced a criterion allowing an unambiguous implementation of CMT in the case of asymmetric couplers having a multi-layer separation zone. The results, in good agreement with experimental data, allowed us to better understand the limitations of the fabricated devices and to propose new structures AlGaAs / AlOx with improved performances. The experimental validation of the proposed designs for both the Si3N4 / SiO2 and AlGaAs / AlOx components is currently in progress.

During the DARPA SCENICC program, J. Ford, et al., demonstrated that CFBs provide a compelling route to compact, wide angle imagers. Monocentric lenses readily provide diffraction-limited images over wide field but onto a hemispherically curved image surface. They demonstrated visible CFBs can be tapered, cut and polished to relay curved images to flat sensors. We have shown that this provides a volumetric imaging efficiency a hundredfold larger than bulk optics can produce; a hundred times the resolution in the same volume or a hundred times less volume for the same resolution. Ford's work leveraged commercial fiber bundles available for the visible spectrum based on silica. We have developed hybrid fiber bundles using step-index confinement between chalcogenide glass cores and polymer cladding with high index-contrast. The high contrast is necessary to provide tight confinement to the high-index As-Se core with minimal crosstalk between closely spaced cores. Tight confinement also minimizes absorption losses in the PEI polymer cladding. The high contrast of this system also provides a large NA to optimize coupling into the CFB from fast lenses. We introduce disorder into the core radius as a mechanism to further decouple adjacent cores, reduce crosstalk and increase fill-factor. We present coupled-mode theory, modal crosstalk superposition, and finite-element modelling to quantify coupling losses and crosstalk as a function of geometry and disorder. We fabricated preforms, drew small fiber bundles and characterized optical properties of the bundles to aid scale-up to megapixel MWIR CFBs.