This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations. The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials. The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3  waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer. From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform. With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors. / <p>QC 20141114</p>

Full wave analysis of microstrip lines at microwave frequencies is performed by using method of moments in conjunction with closed-form spatial domain Green&rsquo / s functions. The Green&rsquo / s functions are in general Sommerfeld-type integrals which are computationally expensive. To improve the efficiency of the technique, Green&rsquo / s functions are approximated by their closed-forms. Microstrip lines are excited by arbitrarily located current sources and are terminated by complex loads at both ends. Current distributions over microstrip lines are represented by rooftop basis functions. At first step, the current distribution over a single microstrip line is calculated. Next, the calculation of the current distributions over coupled microstrip lines is performed. The technique is then, applied to directional couplers. Using the current distributions obtained by the analysis, the scattering parameters of the structures are evaluated by using Prony&rsquo / s method. The results are compared with the ones gathered by using simulation software tools, CNL/2&trade / and Agilent Advanced Design System&trade / (ADS).

Thesis, (M.E.?)-- University of Adelaide, Dept. of Engineering, 1958. / Typewritten.

This semestral thesis focuses on the circuit design of the repeater for PLC communication in order to achieve greater distance in communication. It can also serve as a bridge for a separate modem device power grid. In this work we discuss the involvement of individual assembly parts repeater and proposed method of connection.

[pt] Neste trabalho, o Método dos Elementos Finitos é aplicado na análise eletromagnética de estruturas coaxiais circularmente simétricas excitadas pelo modo TEM. A representação do campo magnético é feita através da associação de funções base polinomiais de diferentes ordens a grades que possuem elementos triangulares ou retangulares. Este trabalho apresenta um estudo comparativo entre as diversas possibilidades de associações função base e elemento, considerando o tempo de processamento computacional e a precisão exigida na simulação. A técnica é aplicada na análise de dispositivos de acoplamento entre diferentes guias coaxiais usualmente empregados em antenas de banda larga. Para validar os resultados do algoritmo, os resultados obtidos nas diversas etapas são comparados com aqueles obtidos via Método de Casamento de Modos. Além disto, a técnica é empregada para avaliar a possibilidade de utilização de dispositivos de inspeção de tubulação que utiliza uma onda TEM de alta freqüência. A onda TEM é excitada no interior da tubulação de forma que variações em suas paredes, nas condições de contorno dos campos, produzam alterações nas características de propagação, que serão detectadas e associadas às anomalias de suas paredes internas. Estes dispositivos de inspeção são empregados na indústria de petróleo e gás. / [en] In this work, the Method of Finite Element is applied in the electromagnetic analysis of circularly symmetrical coaxial structures excited by TEM mode. The representation of the magnetic field is made through the association of polynomial basis functions of different orders associated in the grids made of triangular or rectangular elements. This work presents a comparative study between different possibilities of association between basis functions and element, considering the computational time and the accuracy yielded by the simulation. The technique is applied in the electromagnetic analysis of coupling devices used to connect different coaxial waveguides operating at microwave frequencies. To validate the algorithm developed in this work, the MEF results are compared with those obtained by employing Method of Mode Matching (MMM). Moreover, the technique is also employed to evaluate the possibility of use of TEM wave highfrequency for inspection of metallic pipelines. The TEM wave is excited inside cylindrical metallic pipes and anomalies in the metallic walls are associated to the changes in the propagation characteristics. These inspection devices are intensively used in the industry of oil and gas.

As cargas transportadas pelas ferrovias têm aumentado consideravelmente nos últimos anos, tanto pela capacidade individual do vagão como pela quantidade numa mesma composição. Após simulações e análise de dados obtidos em vagões instrumentados, uma das maiores operadoras logísticas do país observou que seus Sistemas de Choque e Tração estão sendo submetidos a esforços longitudinais considerados extremos. Desta forma, os trens formados por vagões do tipo GDU (capacidade de 118 t) estão limitados a uma quantidade de apenas 122 vagões, perdendo produtividade em relação aos trens formados por vagões do tipo GDT (capacidade de 110 t), os quais vêm circulando com 134 vagões. Em função das cargas extremas e consequente redução da produtividade nos trens, o Cliente solicita um trabalho conjunto para o desenvolvimento de um Sistema de Choque e Tração que torne possível a formação dos trens de minério com 134 vagões do tipo GDU. Desta forma, foi desenvolvido, como alternativa ao aço convencional, um aço baixa liga com desempenho superior, protótipos dos componentes citados para ensaios de campo e respectivos corpos de prova, validados por ensaios laboratoriais, bem como os parâmetros tecnológicos do produto e do processo. Os resultados obtidos são um aumento do Limite de Resistência, Limite de Escoamento, Tenacidade e Vida em Fadiga da ordem de 18% (em função da Temperatura de Revenido adotada), com a manutenção das características de Dutilidade (Alongamento e Redução de Área). / Loads transported by rail have increased considerably in recent years, both for individual freight car capacity and total train tonnage. Following data analysis and simulations obtained in instrumented freight cars, one of the largest logistics operators in the country noted that its Draft Gear Systems are being subjected to longitudinal efforts considered extreme. Thus, trains consisting of cars type GDU (118 ton capacity) have been limited to a quantity of only 122 cars, losing productivity gains regarding trains formed by cars type GDT (110 ton capacity), which circulate with 134 cars. Because of the extreme loads and consequential reduction in productivity of the trains, the Client requests a joint work for the development of a Draft Gear System that enables the formation of ore trains with 134 cars of type GDU. Thus, an alternative to the conventional steel, a low-alloy steel with superior performance was developed from which prototypes of the applicable components for field trials and respective test coupons were produced. This has been validated by laboratory tests, as well as the technological parameters of product and process. The results have indicated an increase in Tensile Strength, Yield Strength, Toughness and Fatigue Life of approximately 18% (depending on Tempering temperature adopted) while maintaining the characteristics of Ductility (Elongation and Area Reduction).

O incessante aumento do volume de informações produzido por uma sociedade cada vez mais informatizada tem elevado drasticamente os requisitos quanto ao desenvolvimento de dispositivos capazes de suportar velocidades de operação cada vez mais elevadas em tamanhos cada vez mais reduzidos. No entanto, a contínua redução do tamanho desses dispositivos, celebrado através da lei de Moore, também produz um indesejável aumento na produção de calor durante a operação dos mesmos, comprometendo seu desempenho global. Uma alternativa promissora para aliviar, ou mesmo superar, estas limitações é oferecida pelos dispositivos ópticos integrados. No entanto, todo esse avanço esbarrava no fato de que as dimensões de tais dispositivos estavam restringidas fundamentalmente ao que é largamente conhecido como limite de difração (LD). Uma maneira de contornar essa limitação é obtida através da utilização de Plásmon Poláritons de Superfície, ou SPPs, que, de maneira simplificada, são ondas que se propagam ao longo da superfície de um condutor depositado sobre um dielétrico. Estas são essencialmente ondas de luz que são localizadas na superfície por causa de sua interação com os elétrons livres do condutor. Nesta interação, os elétrons livres respondem coletivamente oscilando em ressonância com a onda de luz. No presente trabalho, o fenômeno de geração de SPPs é estudado teoricamente e aplicado na modelagem de diversas estruturas de interesse científico e tecnológico, tais como acopladores direcionais e ressoadores. O objetivo principal é a obtenção de estruturas capazes de proporcionar propagação de SPPs por longas distâncias, permitindo, assim, estender ainda mais o leque de possíveis aplicações. As estruturas são investigadas prioritariamente no COMSOL Multiphysics, um aplicativo baseado em elementos finitos que permite solução vetorial de problemas eletromagnéticos. Os resultados obtidos até o momento permitem afirmar que o conceito de SPP de longa distância (long range SPP, LRSPP) podem ser aplicados com sucesso a estruturas geometricamente complexas como os ressoadores em anel e acopladores direcionais. / The continuous growth of knowledge produced by a society with increasing access to information technologies has demanded the development of communication devices capable of supporting high processing speeds at more and more reduced sizes. Nevertheless, the continuous reduction of the size of these devices, celebrated by the Moore\'s law, has also produced an undesirable increase of heat produced during the operation of the device itself, compromising its overall performance. A promising alternative to alleviate, or even overcome, these limitations has been offered by photonic integrated circuits. However, all the advance of photonic devices was restricted to what is known as diffraction limit. A fascinating way of circumventing this limit is now available to the scientific community, and consists in the generation of Surface Plasmon Polariton (SPP) waves. In a simplified manner, SPP waves are waves that propagate along a metal/dielectric interface. These waves are essentially localized at the metal/dielectric interface because of the interaction of light with free electrons of the metal. In this interaction, the free electrons respond collectively and oscillate resonantly with the incident light. In the present work, the phenomenon of SPP generation is theoretically investigated and applied to the modeling of several structures, such as directional couplers and resonators. The primary goal of this work is to design structures capable propagating SPP waves for long distances, known as long range SPP (LRSPP). The structures are investigated mostly with COMSOL Multiphysics, a finite elements based software that allows for the vectorial solution of electromagnetic problems. The results obtained so far are extremely encouraging, and prove that the LRSPP concept can be successfully applied to geometrically complex structures, such as couplers and ring resonators.

Soliton states in three coupled optical waveguide systems were studied: two linearly coupled waveguides with quadratic nonlinearity, two linearly coupled waveguides with cubic nonlinearity and Bragg gratings, and a quadratic nonlinear waveguide with resonant gratings, which enable three-wave interaction. The methods adopted to tackle the problems were both analytical and numerical. The analytical method mainly made use of the variational approximation. Since no exact analytical method is available to find solutions for the waveguide systems under study, the variational approach was proved to be very useful to find accurate approximations. Numerically, the shooting method and the relaxation method were used. The numerical results verified the results obtained analytically. New asymmetric soliton states were discovered for the coupled quadratically nonlinear waveguides, and for the coupled waveguides with both cubic nonlinearity and Bragg gratings. Stability of the soliton states was studied numerically, using the Beam Propagation Method. Asymmetric couplers with quadratic nonlinearity were also studied. The bifurcation diagrams for the asymmetric couplers were those unfolded from the corresponding diagrams of the symmetric couplers. Novel stable two-soliton bound states due to three-wave interaction were discovered for a quadratically nonlinear waveguide equipped with resonant gratings. Since the coupled optical waveguide systems are controlled by a larger number of parameters than in the corresponding single waveguide, the coupled systems can find a much broader field of applications. This study provides useful background information to support these applications.

The main objectives of this thesis were to develop a lowtemperature PECVD process suitable for optoelectronicintegration, and to optimize silica glass composition forUV-induced modifications of a refractive index in PECVDfabricated planar devices. The most important achievement isthe successful development of a low temperature silicadeposition, which for the first time makes it is possible tofabricate good quality low loss integrated components whilekeeping the temperature below 250oC during the entirefabrication process. Two strong absorption peaks thatappear at1.5 mm communication window due to N-H and Si-H bonds have beencompletely eliminated by process optimization. This openspossibilities for monolithic integration with other,temperature sensitive devices, such as semiconductor lasers anddetectors, or polymer-based structures on the common siliconplatform. PECVD technology for low loss amorphous silicon inapplication to SiO2/Si based photonic crystal structures hasbeen also optimized to remove hydrogen incorporated during thedeposition process, responsible for the porosity of thedeposited material and creation of similar to silica absorptionbands. Change of the refractive index of germanium doped silicaunder UV irradiation is commonly used for fabrication of UVinduced fiber Bragg gratings. Here we describe our achievementsin fabrication of fiber Bragg gratings and their application todistributed sensor systems. Recently we have built up a laserlab for UV treatment in application to planar technology. Wehave demonstrated the high photosensitivity of PECVD depositedGe-doped glasses (not thermally annealed) even without hydrogenloading, leading to a record transmission suppression of 47dBin a Bragg grating photoinduced in a straight buried channelwaveguide. We have also used a UV induced refractive indexchange to introduce other device modifications or functions,such as phase shift, wavelength trimming and control ofpolarization birefringence.The developed low temperature technology and the UVprocessing form a unique technology platform for development ofnovel integrated functional devices for optical communicationsystems. A substantial part of the thesis has been devoted tostudying different plasma deposition parameters and theirinfluence on the optical characteristics of fabricatedwaveguides to find the processing window giving the besttrade-off between the deposition rate,chamber temperatureduring the process, optical losses and presence of absorptionbands within the interesting wavelength range. The optimalconditions identified in this study are low pressure (300-400mTorr), high dilution of silane in nitrous oxide and high totalflow (2000 sccm), low frequency (380 KHz) RF source and high RFpower levels (800-1000 W). The thesis provides better understanding of the plasmareactions during the deposition process. RF Power is the keyparameter for increasing the rate of surface processes so as toaccommodate each atomic layer in the lowest energy statepossible. All the process conditions which favor a moreenergetic ion bombardment (i.e. low pressure, low frequency andhigh power) improve the quality of the material, making it moredense and similar to thermal oxide, but after a certain pointthe positive trend with increasing power saturates. As theenergy of the incoming ion increases, a competing effect setsin at the surface: ion induced damage and resputtering. Finally, the developed technologies were applied for thefabrication of some test and new concept devices for opticalcommunication systems including multimode interference (MMI)-based couplers/splitters, state-of-the-art arrayed waveguidegrating-based multi/ demultiplexers, the first Bragg gratingassisted MMI-based add-drop multiplexer, as well as moreresearch oriented devices such as a Mach-Zehnder switch basedon silica poling and a Photonic Crystal-based coupler. <b>Keywords:</b>silica-on-silicon technology, PECVD, plasmadeposition, photonic integrated circuits, planar waveguidedevices, UV Bragg gratings, photosensitivity, arrayed waveguidegratings, multimode interference couplers, add-dropmultiplexers.

<p>The main objectives of this thesis were to develop a lowtemperature PECVD process suitable for optoelectronicintegration, and to optimize silica glass composition forUV-induced modifications of a refractive index in PECVDfabricated planar devices. The most important achievement isthe successful development of a low temperature silicadeposition, which for the first time makes it is possible tofabricate good quality low loss integrated components whilekeeping the temperature below 250oC during the entirefabrication process. Two strong absorption peaks thatappear at1.5 mm communication window due to N-H and Si-H bonds have beencompletely eliminated by process optimization. This openspossibilities for monolithic integration with other,temperature sensitive devices, such as semiconductor lasers anddetectors, or polymer-based structures on the common siliconplatform. PECVD technology for low loss amorphous silicon inapplication to SiO2/Si based photonic crystal structures hasbeen also optimized to remove hydrogen incorporated during thedeposition process, responsible for the porosity of thedeposited material and creation of similar to silica absorptionbands.</p><p>Change of the refractive index of germanium doped silicaunder UV irradiation is commonly used for fabrication of UVinduced fiber Bragg gratings. Here we describe our achievementsin fabrication of fiber Bragg gratings and their application todistributed sensor systems. Recently we have built up a laserlab for UV treatment in application to planar technology. Wehave demonstrated the high photosensitivity of PECVD depositedGe-doped glasses (not thermally annealed) even without hydrogenloading, leading to a record transmission suppression of 47dBin a Bragg grating photoinduced in a straight buried channelwaveguide. We have also used a UV induced refractive indexchange to introduce other device modifications or functions,such as phase shift, wavelength trimming and control ofpolarization birefringence.The developed low temperature technology and the UVprocessing form a unique technology platform for development ofnovel integrated functional devices for optical communicationsystems.</p><p>A substantial part of the thesis has been devoted tostudying different plasma deposition parameters and theirinfluence on the optical characteristics of fabricatedwaveguides to find the processing window giving the besttrade-off between the deposition rate,chamber temperatureduring the process, optical losses and presence of absorptionbands within the interesting wavelength range. The optimalconditions identified in this study are low pressure (300-400mTorr), high dilution of silane in nitrous oxide and high totalflow (2000 sccm), low frequency (380 KHz) RF source and high RFpower levels (800-1000 W).</p><p>The thesis provides better understanding of the plasmareactions during the deposition process. RF Power is the keyparameter for increasing the rate of surface processes so as toaccommodate each atomic layer in the lowest energy statepossible. All the process conditions which favor a moreenergetic ion bombardment (i.e. low pressure, low frequency andhigh power) improve the quality of the material, making it moredense and similar to thermal oxide, but after a certain pointthe positive trend with increasing power saturates. As theenergy of the incoming ion increases, a competing effect setsin at the surface: ion induced damage and resputtering.</p><p>Finally, the developed technologies were applied for thefabrication of some test and new concept devices for opticalcommunication systems including multimode interference (MMI)-based couplers/splitters, state-of-the-art arrayed waveguidegrating-based multi/ demultiplexers, the first Bragg gratingassisted MMI-based add-drop multiplexer, as well as moreresearch oriented devices such as a Mach-Zehnder switch basedon silica poling and a Photonic Crystal-based coupler.</p><p><b>Keywords:</b>silica-on-silicon technology, PECVD, plasmadeposition, photonic integrated circuits, planar waveguidedevices, UV Bragg gratings, photosensitivity, arrayed waveguidegratings, multimode interference couplers, add-dropmultiplexers.</p>