Dissertations / Theses: 'Electro-optical modulation'

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Thorn, Andrew Peter. "Electro-optical modulation in III-V semiconductors." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46578.

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Riedel, Christoph Alexander. "Transparent conductive oxide based hybrid nanostructures for electro-optical modulation." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/420940/.

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In the last decades, plasmonic resonant nanoantennas have created interest in a wide range of research fields that deal with light confinement on the nanoscale. One promising new research branch involves electrically switchable optical properties, which are scaled down to sub-μm size using plasmonic structures. In this thesis, samples with antenna structures whose resonances can be electrically modulated were designed, fabricated and characterised both electrically and optically. A comprehensive analytical study on the interaction of carrier modulation and optical antennas showed that shifts of the resonance wavelength depend on the antenna aspect ratio and material, and are enhanced if the surrounding medium’s permittivity is near zero. The simulation capabilities of the properties of transparent conductive oxides were successfully utilised to design an ultrathin optical solar reflector that selectively radiates visible and nearinfrared light while strongly absorbing mid-infrared light. The measured solar absorptance was 0.12 and the IR emissivity 0.79. Such selective reflectors can replace currently-used metallised quartz tiles to reduce launch costs of spacecraft. Combining electrical and optical simulation models with nanoscale resolution, a novel modulator structure was designed. By directly electrically addressing nanoantennas, a modulator was enabled to perform in transmission additionally to reflection. Reducing the ITO volume to a gap-filling removed negative impacts of the ITO background, so that the resulting modulator could freely shift the resonance of the antenna. The final structure showed a greatly enhanced amplitude modulation of 45% and a resonance shift of 38nm at 1550nm with an applied electric field of 1Vnm⁻¹. Fabricated structures showed that the placing of an ITO gap-loading can be achieved by taking into account height alignment errors of current e-beam systems. Experiments on a planar electrical modulator with a TiN-HfO2-ITO stack showed first electro-optical modulation results, which can benefit from the design developed with the simulation model. The promising results obtained in this thesis open a new pathway for electro-plasmonic modulation in a variety of structures such as tunable reflectors and transmitters in free space or on silicon waveguides.

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Chretien, Jacques. "Développement de micro-modulateurs électro-optiques à base de matériaux à coefficients géants." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2014/document.

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Cette thèse a pour but de développer de nouveaux procédés de fabrication dansle cadre de la réalisation de composants électro-optiques basés sur l’utilisation dematériaux à coefficients géants.A travers le développement de procédés de mises en forme inovants, différentsaspects théoriques et expérimentaux ont été abordés notamment avec la mise enplace d’un procédé de repolarisation dédié au Niobate de Strontium Baryum
The objective of this thesis is to develop new manufacturing processes within theframework of the realization of electro-optical components based on specifics materialswith giant electro-opticals coefficients.Through the development of inovative methods, various theoretical and experimentalaspects were addressed, in particular through the implementation of a repolarizationprocess dedicated to Strontium Barium Niobate

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Allibe, Julie. "Développement et intégration de films minces du multiferroïque BiFeO3 pour la modulation électro-optique et le contrôle électrique d'une aimantation." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112091.

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Jacobsson, Fredrik. "DPSK modulation format for optical communication using FBG demodulator." Thesis, Linköping University, Department of Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2307.

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The task of the project was to evaluate a differential phase shift keying demodulation technique by replacing a Mach-Zehnder interferometer receiver with an optical filter (Fiber Bragg Grating). Computer simulations were made with single optical transmission, multi channel systems and transmission with combined angle/intensity modulated optical signals. The simulations showed good results at both 10 and 40 Gbit/s. Laboratory experiments were made at 10 Gbit/s to verify the simulation results. It was found that the demodulation technique worked, but not with satisfactory experimental results. The work was performed at Eindhoven University of Technology, Holland, within the framework of the STOLAS project at the department of Electro-optical communication.

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Pagano, Carlo [Verfasser], and Christian [Akademischer Betreuer] Boit. "Electro optical frequency modulation on silicon integrated circuits with 1300nm and 1064nm laser sources / Carlo Pagano. Gutachter: Christian Boit." Berlin : Technische Universität Berlin, 2015. http://d-nb.info/1069319317/34.

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Nguyen, Giang Thach, and thach nguyen@rmit edu au. "Efficient Resonantly Enhanced Mach-Zehnder Optical Modulator on Lithium Niobate." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070118.162330.

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Photonic links have been proposed to transport radio frequency (RF) signals over optical fiber. External optical modulation is commonly used in high performance RF-photonic links. The practical use of optical fiber to transport RF signals is still limited due to high RF signal loss. In order to reduce the RF signal loss, highly efficient modulators are needed. For many applications, modulators with broad bandwidths are required. However, there are applications that require only a narrow bandwidth. For these narrow-band applications, the modulation efficiency can be improved through the resonant enhancement technique at the expense of reduced bandwidth. The aim of this thesis is to investigate highly efficient Mach-Zehnder optical modulators (MZMs) on Lithium Niobate (LiNbO3) with resonant enhancement techniques for narrow-band RF-photonic applications. This work focuses in particular on analyzing the factors that affect the modulation efficiency through resonant enhancement so that the modulator electrode structure can be optimized for maximum modulation efficiency. A parameter study of the effects of the electrode characteristics on the modulation efficiency of resonantly enhanced modulators (RE-MZM) is provided. From this study, optimum design objectives are identified. Numerical optimization is employed to explore the design trade-offs so that optimal configurations can be found. A sensitivity analysis is carried out to assess the performance of optimal RE-MZMs with respect to the variations of fabrication conditions. The results of these investigations indicate that the RE-MZM with a large electrode gap is the optimal design since it provides high modulation efficiency although the inherent switching voltage is high, and is the most tolerant to the fabrication fluctuations. A highly efficient RE-MZM on X-cut LiNbO3 is practically demonstrated with the resonant enhancement factor of 5 dB when comparing to the unenhanced modulator with the same electrode structure and effective switching voltage of 2 V at 1.8 GHz. The performance of the RF-photonic link using the fabr icated RE-MZM is evaluated. Optimization of RE-MZMs for operating at millimeter-wave frequencies is also reported. Factors that limit the modulation efficiency of an RE-MZM at millimeter-wave frequencies are identified. Novel resonant structures that can overcome these limitations are proposed. Preliminary designs indicate that greatly improved modulation efficiency could be expected.

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Gutiérrez, Campo Ana María. "Development of integrated silicon photonics modulation devices for digital and analog applications." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/33330.

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Silicon photonics is one of the most exciting and fastest growing photonic technologies in recent years. The salient feature of this technology is its compatibility with the mature silicon IC manufacturing based on complementary metal-oxide semiconductor (CMOS) processes widely used in microelectronic industry. Another motivation is the availability of high-quality silicon-on-insulator (SOI) planar waveguide circuits that offer strong optical confinement due to the high index contrast between silicon (n=3.45) and SiO2 (n=1.45). This opens up miniaturization and very large scale integration of photonic devices allowing photonic integrated circuits for a wide range of applications and markets, from optical telecommunications to bio-photonic devices or precise fibre sensors. Optical modulators are key building-blocks for high speed signal transmission and information processing in any photonic interconnection solution. The work developed in this thesis, as part of the objectives of the European project HELIOS in which it is framed, is essentially focused on realizing compact and efficient modulators integrated on silicon chips. The thesis consists of three main chapters as well as the concluding section on the work accomplished. Chapter one is aimed at giving a general description of the benefits of using silicon photonics, showing its challenges and opportunities as well as at giving a deeply overview of all issues related to the electro-optic modulation. Chapter two is devoted to develop silicon modulators with high features for digital applications. Specifically, new optical structures different to the conventional ones are presented with the aim of enhancing the modulation performance or at least several critical parameters in the modulation. Chapter three is dedicated to the analog applications. The concept of microwave photonics is described as well as different researches carried out in the analog scope for application in the field of integrated microwave photonics, all of them using CMOS-compatible electro-optic silicon modulators which validate the potential of silicon photonics as a promising approach for enabling the development of integrated microwave photonics applications. Finally, conclusions on the work realized are provided in Chapter 4.
La fotónica de silicio es una de las tecnologías fotónicas que está experimentando un crecimiento más excitante y rápido en los últimos años. La característica más destacada de esta tecnología es su compatibilidad con las maduras técnicas de fabricación de circuitos integrados de silicio basadas en los procesos ¿complementary metal-oxide semiconductor¿ (CMOS) ampliamente utilizados en la industria microelectrónica. Otra motivación es la disponibilidad de circuitos de guía de ondas planas de silicio sobre aislante (SOI) de alta calidad que ofrecen un fuerte confinamiento óptico debido al alto contraste índices entre el silicio (n=3,45) y el SiO2 (n = 1,45). Esto abre las puertas a la miniaturización y a la integración a gran escala de dispositivos fotónicos lo que resulta en circuitos fotónicos integrados para una amplia gama de aplicaciones y mercados, desde telecomunicaciones ópticas a dispositivos bio-fotónicos o sensores de fibra precisos. Los moduladores ópticos son elementos básicos fundamentales para la transmisión de señales a alta velocidad y el procesado de información en cualquier solución de interconexión fotónica. El trabajo desarrollado en esta tesis, como parte del los objetivos del proyecto Europeo HELIOS en el que está enmarcada, se centra fundamentalmente en realizar moduladores compactos y eficientes, integrados en chips de silicio. La tesis consiste en 3 capítulos principales así como una sección de conclusiones del trabajo conseguido. El capítulo uno está destinado a dar una descripción general de los beneficios del uso de la fotónica de silicio, mostrando sus retos y oportunidades, así como a dar una visión profunda de todos los aspectos relacionados con la modulación electro-óptica. El capítulo dos está dedicado a desarrollar moduladores de silicio de altas prestaciones para aplicaciones digitales. Específicamente, se presentan nuevas estructuras ópticas diferentes a las convencionales con el objetivo de mejorar el rendimiento de la modulación o al menos algunos parámetros críticos en la modulación. El tercer capítulo se dedica a las aplicaciones analógicas. Se describe el concepto de la fotónica de microondas, así como diferentes investigaciones llevadas a cabo en el ámbito analógico para su aplicación en el campo de la fotónica integrada de microondas, todas ellas usando moduladores electro-ópticos de silicio compatibles con los procesos de fabricación CMOS, lo que valida el potencial de la fotónica de silicio como un prometedor enfoque para permitir el desarrollo de aplicaciones de la fotónica integrada de microondas. Por último, las conclusiones sobre el trabajo realizado se proporcionan en el Capítulo 4.
Gutiérrez Campo, AM. (2013). Development of integrated silicon photonics modulation devices for digital and analog applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/33330
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Giuglea, Alexandru, Guido Belfiore, Mahdi Khafaji, Ronny Henker, Despoina Petousi, Georg Winzer, Lars Zimmermann, and Frank Ellinger. "Comparison of Segmented and Traveling-Wave Electro-Optical Transmitters Based on Silicon Photonics Mach-Zehnder Modulators." Institute of Electrical and Electronics Engineers (IEEE), 2018. https://tud.qucosa.de/id/qucosa%3A35393.

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This paper presents a brief study of the two most commonly used topologies - segmented and traveling-wave - for realizing monolithically integrated electro-optical transmitters consisting of Si-photonics Mach-Zehnder modulators and their electrical drivers. To this end, two new transmitters employing high swing breakdown voltage doubler drivers were designed in the aforementioned topologies and compared with regard to their extinction ratio and DC power consumption at the data rate of 30 Gb/s. It is shown that for the targeted data rate and extinction ratio, a considerably lower power consumption can be achieved with the traveling-wave topology than with its segmented counterpart. The transmitters were realized in a 250 nm SiGe BiCMOS electronic-photonic integrated technology.

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Abelard, Clément. "Micro modulateur spatial de lumière transmissif pour modulation de phase et d’amplitude." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAT092/document.

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Le LETI possède un savoir-faire permettant de réaliser des micro modulateurs spatiaux de lumière (Spatial Light Modulators, SLMs) réalisés en technologie microélectronique sur silicium, ayant des très grandes résolutions et de très petits pas de pixels. Le LETI souhaite utiliser une technologie LCD particulière (la technologie IPS) dont d’une part les performances électro-optiques dans le domaine des micro-écrans ne sont pas connues mais d’autre part permet de garder des coûts réduits et de réduire le nombre d’étapes de fabrication. L’objectif de cette thèse est d’évaluer sur la base de simulations puis de réalisations techniques, les performances d’un micro-SLM IPS utilisé en modulation de phase et d’amplitude.Les recherches effectuées au cours de cette thèse portent sur 4 axes d’études. Le premier axe consiste à la recherche et à l’essai d’un logiciel spécifique (LCDMaster) permettant de simuler des cellules à cristaux liquides ainsi que des électrodes flottantes. Le second axe consiste à étudier en fonction du design du pixel et des différents modes d’alignements des cristaux liquides (Homogène, vertical et twisté) avec un pilotage de type IPS, les performances en modulation de phase. Les meilleurs résultats sont obtenus pour un alignement vertical fournissant un déphasage de 2 Pi. De plus, les performances d’un dispositif d’optique adaptative intégrant le SLM étudié ont été investiguées. Le troisième axe d’étude, consiste avec le même logiciel à investiguer sur les performances d’un SLM à cristaux liquide avec un pilotage de type IPS utilisant un alignement homogène en modulation d’amplitude (étude statique et dynamique). Cette étude permet également d’étudier les possibilités de diminution du temps de réponse de la cellule. Cette étude a aboutie à deux designs de SLM. Le premier design avec deux niveaux d’électrodes séparés par un isolant permettant de reproduire un effet type « cage de faraday ». La seconde a permis de diminuer de manière drastique le temps de réponse. Le quatrième axe de recherche consiste à tester des prototypes basés sur ces deux designs pour vérifier les performances obtenues en simulation grâce à un banc de caractérisation électro-optique. Des résultats concordants ont étés obtenus et de nouveaux types de SLM à pilotage IPS proposant un temps de rafraichissement rapides se rapprochant de l’état de l’art ont donc pu être désignés et caractérisés
LETI possesses an expertise allowing to realize Spatial Light Modulators (SLMs) made in microelectronic technology on silicon, having very high resolutions and very small pixel steps. LETI wishes to use a specific LCD technology (IPS technology), on the one hand the electro-optical performances in the field of micro-display had to be investigated but on the other hand allows to keep costs down and reduce the number of manufacturing steps. The objective of this thesis is to evaluate on the basis of simulations and technical achievements, the performance of a micro-SLM IPS used in phase modulation and amplitude.Our investigations have been carried out on four major areas of study. The first axis is the search and testing of a specific software (LCDMaster) to simulate liquid crystal cells and floating electrodes. The second axis according to different designs of pixel and the different liquid crystal alignment modes (Homogeneous, vertical and twisted) with an IPS type control, to investigate the performances in modulation phase. The best results were obtained for a vertical alignment providing a phase shift of 2π. In addition, the performance of an adaptive optics device integrating the studied SLM has been investigated. The third axis of study focused on the performance investigation of a liquid crystal SLM with an IPS-type control using a homogeneous alignment in amplitude modulation (static and dynamic study). This study also makes it possible to study the possibilities of reducing the response time of the cell. It resulted in two SLM designs. The first design with two levels of electrodes separated by an insulator to reproduce a Faraday type effect. The second has drastically reduced the response time. The fourth area of research consists in testing prototypes based on these two designs to validate the performances obtained in simulation. Concordant results have been obtained and new types of IPS-controlled SLMs with state-of-the-art refreshing times have thus been designated and characterized

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Simões, Fábio Donati. "Estudo do impacto do gorjeio (chirp) de transiente sobre o desempenho de sistemas de transmissão óptica com pulsos NRZ." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-04072008-090547/.

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Formatos de modulação com capacidade de ajuste às condições variáveis de propagação são de interesse para uso em redes ópticas reconfiguráveis. Alterações nos níveis de potência e no mapa de dispersão afetam o desempenho de sistemas de transmissão, limitando o alcance e a capacidade de reconfiguração da rede. Fornecer capacidade de ajuste dinâmico ao sinal transmitido, sem usar sistemas complexos de modulação ou de compensação variável de dispersão, é uma solução eficaz para se obter rendimento ótimo nas diversas condições de propagação na rede. Esta característica também é útil na instalação de redes convencionais, poupando tempo e reduzindo custos. Neste trabalho é proposto o formato de modulação NRZ com gorjeio sincronizado com o sinal como alternativa para sobrepujar as limitações impostas pelas redes reconfiguráveis. O sistema proposto tem o atrativo de permitir, além da capacidade de adaptação, a possibilidade de integração dos componentes ópticos do modulador num mesmo substrato. O desempenho do formato de modulação proposto foi analisado em diversas condições de propagação para sistemas a 10 Gbit/s, tanto em sistemas ponto-a-ponto como de longas distâncias. Esta análise foi feita por meio de modelagem matemática, simulações numéricas e experimentos em laboratório. Foi demonstrada a capacidade de ajuste a diversos mapas de dispersão e seus limites, bem como a compensação de efeitos da automodulação de fase causados por alterações no nível da potência do sinal.
Modulation formats with adjustment capability to the variable propagation conditions are of interest in reconfigurable optical networks. Changes in optical power levels and dispersion compensation map affect the transmission system performance, limiting the range and the network reconfiguration capability. To provide dynamical adjustment capability to the transmitted signal, using neither complex modulation systems nor variable dispersion compensation, is an effective solution to obtain optimal performance within the diverse network propagation conditions. This characteristic is also useful during conventional networks installation, saving time and reducing costs. In this work it is proposed the NRZ modulation format with signal synchronized chirp as an alternative to overcome the limitations imposed by the reconfigurable networks. The proposed system has the benefit of allowing, more than adaptation capability, the possibility of integration of the optical modulator\'s components in the same substrate. The proposed modulation format was analyzed under diverse propagation conditions for 10 Gbit/s, in point-to-point as well as long-haul systems. This analyses war performed by mathematical modeling, numerical simulations and laboratorial experiments. It was demonstrated the adjustment capability for diverse dispersion compensation maps and its limits as well as the compensation of the self-phase modulation effects due to changes in optical power levels.

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Roth, Matthias [Verfasser], Klaus [Gutachter] Janschek, and Wolfgang [Gutachter] Osten. "Contributions to the design of Fourier-optical modulation systems based on micro-opto-electro-mechanical tilt-mirror arrays / Matthias Roth ; Gutachter: Klaus Janschek, Wolfgang Osten." Dresden : Technische Universität Dresden, 2020. http://d-nb.info/1227202296/34.

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Barbarini, Elisa Signoreto. "Análise óptica de sistemas eletro-ópticos por meio do cálculo da função de transferência de modulação." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18152/tde-20062012-151937/.

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Um grande número de equipamentos utilizam sistemas ópticos ou eletro-ópticos em suas estruturas, dentre esses equipamentos tem-se os microscópios, telescópios, equipamentos médicos, câmeras de satélites, entre outros. Com isso a necessidade de métodos e ferramentas que auxiliem na determinação do desempenho e da qualidade dos sistemas ópticos é crescente. Um dos métodos mais utilizados para realizar a análise de sistemas ópticos é a determinação da Função de Transferência de Modulação (Modulation Transfer Function - MTF). A MTF representa uma verificação quantitativa e direta da qualidade da imagem, e, além disso, é um teste objetivo que pode ser utilizado em sistemas ópticos concatenados. Esse trabalho apresenta a implementação de um software, denominado de SMTF (Software Modulation Transfer Function), para cálculo da MTF de equipamentos eletro-ópticos. O software foi utilizado para realizar o cálculo da MTF do Retinógrafo Digital, Imageador Termal e Microscópio Cirúrgico Oftalmológico. A informação da MTF auxilia na análise do alinhamento e medição da qualidade óptica, e também define o limite de resolução dos sistemas ópticos, por meio do gráfico da MTF. Os resultados obtidos, com o Retinógrafo e o Imageador Termal, foram comparados com os valores teóricos adquiridos pelo Zemax, que é um software utilizado para desenvolvimento e análise de lentes ou conjuntos ópticos. Já para o Microscópio os resultados obtidos da MTF foram comparados com os resultados obtidos pela MTF medida do Microscópio marca Zeiss, considerado como padrão de qualidade de Microscópios Oftalmológicos. Os resultados obtidos demonstram que o software apresentou ótimo desempenho permitindo uma análise direta e objetiva do comportamento de sistemas ópticos. Com auxílio do software foi feito o alinhamento do Retinógrafo Digital e do Imageador Termal e foi verificada a qualidade da imagem do Microscópio Cirúrgico Oftalmológico.
A number of devices use optics or electro-optics in their structures, such as microscopes, telescopes, medical equipments, satellites cameras, among others. The need for methods and tools that assist in determining the performance and quality of optical systems is increasing. One of the methods most used to perform analysis of optical systems is to measure the Modulation Transfer Function (MTF). The MTF represents a direct and quantitative verification of the image quality, and moreover, it is an objective test that can be used in concatenated optical systems. This paper presents the implementation of software, called SMTF (Software Modulation Transfer Function), in order to calculate the MTF of electro-optical systems. The software was used for calculating the MTF of Digital Fundus Camera, Thermal Imager and Ophthalmologic Surgery Microscope. The information MTF aids the analysis of alignment and measurement of optical quality, and also defines the limit resolution of optical systems, from the graph of MTF. The results obtained with the Fundus Camera and de Thermal Imager were compared with the theorical values acquired by the Zemax, wich is a software used for analysis and development of optical assemblies or lenses. For the Microscope, the results were compared with MTF measured of Microscope Zeiss model, which is the quality standard of ophthalmological microscope. The results show that the software has a good performance by allowing a straightforward analysis of the behavior of optical systems. With the aid of the software was made to align the Fundus Camera and the Thermal Imager and the image quality of Surgical Microscope Ophthalmology was verified.

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Chaisakul, Papichaya. "Ge/SiGe quantum well devices for light modulation, detection, and emission." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00764154.

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This PhD thesis is devoted to study electro-optic properties of Gemanium/Silicon-Germanium (Ge/SiGe) multiple quantum wells (MQWs) for light modulation, detection, and emission on Si platform. It reports the first development of high speed, low energy Ge/SiGe electro-absorption modulator in a waveguide configuration based on the quantum-confined Stark effect (QCSE), demonstrates the first Ge/SiGe photodiode with high speed performance compatible with 40 Gb/s data transmission, and realizes the first Ge/SiGe light emitting diode based on Ge direct gap transition at room temperature. Extensive DC and RF measurements were performed on each tested prototype, which was realized using the same epitaxial growth and fabrication process. Simple theoretical models were employed to describe experimental properties of the Ge/SiGe MQWs. The studies show that Ge/SiGe MQWs could potentially be employed as a new photonics platform for the development of a high speed optical link fully compatible with silicon technology.

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Neves, Daniel Marchesi de Camargo. "Ressoadores WGM baseados em grafeno como plataforma para moduladores de eletro-absorção." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/18/18155/tde-07082015-100910/.

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O objetivo deste trabalho é investigar a aplicação ressoadores WGM (Whispering-Gallery Mode) em plataforma SOI (silicon-on-insulator) baseados em grafeno como candidatas potenciais para aplicações como moduladores de eletro-absorção. O grafeno apresenta variação de condutividade considerável quando submetido a uma aplicação de tensão, o que reflete na parte imaginária de seu índice de refração (relacionada às perdas de propagação). Com isso, é possível atribuir estados ligado e desligado (on-off) que conferem ao dispositivo sua característica de modulação óptica. A geometria utilizada é do tipo anel, o que permite uma elevada seletividade em frequência possibilitando, assim, uma grande profundidade de modulação. As simulações foram realizadas no software de elementos finitos COMSOL Multiphysics, o qual é bastante apropriado para a definição das diferentes figuras de mérito a serem utilizadas para a caracterização do desempenho do modulador.
The goal of this work is to investigate SOI (silicon on insulator) WGM (Whispering-Gallery Modes) resonators based on graphene as potential candidates for electro-absorption modulator applications. Graphene conductivity varies substantially when submitted to an applied voltage, which reflects directly in the imaginary part of its refractive index (responsible for the propagation losses). Therefore, it is possible to assign on-off states that render the device its optical modulation characteristics. The geometry adopted for the design is the ring type, which allows high frequency selectivity and modulation depth. The simulations were carried out in the finite elements software COMSOL Multiphysics, which is quite appropriate for the definition of the different figure of merits to be used in the modulator characterization.

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Leroy, Floriane. "Etude des propriétés électro-optiques des couches minces de Ba1-xSrxTiO3 pour la modulation optique." Phd thesis, Université de Valenciennes et du Hainaut-Cambresis, 2012. http://tel.archives-ouvertes.fr/tel-00749716.

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Le développement de nouveaux matériaux est essentiel dans la réalisation de capteurs de petites dimensions et pour les composants micro-nano-optoélectroniques. Les matériaux à base d'oxydes en sont de bons candidats. Ce travail de thèse a concerné la synthèse de matériaux ferroélectriques tels le BaTiO3 (BTO) et le Ba1-xSrxTiO3 (BST), associés à des électrodes inférieures et supérieures en oxyde d'indium-d'étain (ITO), tous déposés par pulvérisation cathodique RF (radio fréquence). Nous nous sommes concentrés sur la relation existante entre les propriétés optiques et électro-optiques de guide d'ondes et l'orientation cristalline, la couche d'interface ainsi que la nature du substrat. Après la caractérisation des propriétés structurales, nous avons évalué les propriétés optiques de ces matériaux par la technique du couplage par prisme pour une gamme de longueurs d'ondes de l'UV au proche IR. Les résultats ont montré un bon confinement de la lumière dans le film, avec des pertes planaires de propagation optique de l'ordre de 3 dB/cm aux longueurs d'onde télécoms, résultats à l'état de l'art pour ces matériaux.Cette méthode de couplage optique a permis de mettre en évidence les propriétés électro-optiques du BTO et du BST dans cette même gamme de longueurs d'onde et pour les deux polarisations optiques, à partir de la variation des spectres de réflectivité. Si le BTO a montré un coefficient r33 de 23 pm/V aux longueurs d'onde télécoms, nous avons mesuré autour de 19 pm/V pour le BST(70/30).

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Trouillet, Alain. "Réalisation de guides optiques plans en polymères non linéaires : application à la modulation électrooptique de plasmons de surface à faibles pertes." Saint-Etienne, 1994. http://www.theses.fr/1994STET4003.

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Ce mémoire présente l'étude des propriétés optiques non linéaires de matériaux polymères et met en évidence l'intérêt d'un plasmon de surface à faibles pertes pour réaliser un modulateur électrooptique en optique intégrée. Après une présentation générale des propriétés optiques non linéaires dans les polymères, nous décrivons la caractérisation de composés nouveaux obtenus par copolymérisation du styrène avec des comonomères non linéaires dérivés du CMS (chlorométhylstyrène) ou bien du HEMA (hydroxyéthylméthacrylate). Des coefficients non linéaires d33 compris entre 1 et 13 pm/v ont été déterminés en réalisant des expériences de doublement de fréquence, à 1064 nm, en transmission au travers de guides plans déposés sur verre et orientés par corona-poling. Nous avons étudié l'évolution temporelle de ces propriétés. Dans une seconde partie, nous présentons l'étude de modulateurs électrooptiques dont le matériau actif est un polymère et dans lesquels un film métallique sert à la fois d'électrode et de support pour l'onde optique qui est un plasmon de surface. Nous avons utilisé ce mode particulier, dont l'origine est associée à l'excitation d'oscillations de plasma du milieu métallique, pour mesurer le coefficient électrooptique r33 a 632. 8 nm. Un modulateur dans lequel une électrode mince d'argent est encadrée par deux polymères d'indices voisins est susceptible de fonctionner avec des tensions de commande de quelques volts en excitant un plasmon de surface à faibles pertes. Des simulations numériques et une étude expérimentale sont présentées

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18

Gelsen, Olaf Michael. "Electro-modulation spectroscopy of arylene vinylene polymers." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283950.

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Pascal, Simon. "Conception et étude de chromophores polyméthines pour l'optique non-linéaire dans le proche infrarouge." Thesis, Lyon, École normale supérieure, 2014. http://www.theses.fr/2014ENSL0909.

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L’objectif de cette thèse consistait à développer des colorants de la famille des polyméthines absorbant dans le proche infrarouge et présentant des propriétés d’optique non-linéaire (ONL) prononcées. De nouveaux chromophores ont été préparés et leurs propriétés spectroscopiques ont été systématiquement étudiées afin d’établir des relations structures-propriétés. Cette stratégie a permis l’identification des facteurs permettant d’exalter la réponse ONL des polyméthines et de prédire leur comportement face à de subtiles modifications structurales. Trois familles de colorants ont été préparées : des monométhines aza-dipyrrométhènes de bore, des heptaméthines symétriques ainsi que des heptaméthines dissymétriques.Dans un premier temps, des aza-bodipys possédant des groupements donneurs périphériques sont synthétisés. Une étude spectroscopique approfondie permet d’identifier les structures présentant une absorption à deux photons importante en vue d’applications en limitation optique aux longueurs d’onde des télécommunications (1500 nm). Le chapitre suivant a pour but de rationaliser les équilibres de la limite cyanine. L’étude de la substitution centrale de nombreux dérivés heptaméthines a permis de moduler leurs propriétés optiques sur une large gamme spectrale et de mettre en évidence une nouvelle structure électronique limite de type bis-dipôle. Parmi cette famille de colorants, des dérivés keto-heptaméthines ont été utilisées en imagerie biologique (cellules et cerveau) par microscopie non-linéaire. Enfin, l’élaboration de structures heptaméthines dissymétriques originales est détaillée dans le dernier chapitre. Ces chromophores ont révélé des propriétés ONL du second ordre idéales pour des applications en modulation électro-optique
The aim of this thesis consisted in developing dyes from the polymethine family absorbing in the near-infrared (NIR) region and featuring pronounced nonlinear optical (NLO) properties. Several new chromophores have been prepared and their spectroscopic properties have been systematically investigated in order to establish structure-properties relationships. This strategy has permitted the identification of the factors that enhance the NLO response of polymethines and allowed the prediction of their optical behaviour depending on subtle structural modifications. Three families of dyes have been prepared and investigated: boron aza-dipyrro-monomethines (aza-bodipys), symmetrical heptamethines and unsymmetrical heptamethines.In a first time, aza-bodipys possessing electro-donating peripherical substituants has been synthesized. A detailed spectroscopic study allow the identification of structures that present a high two-photon absorption (TPA), towards optical limiting applications at telecommunication wavelengths (1500 nm). The next chapter rationalizes the equilibrium surrounding the cyanine limit. The study of the central substitution of several heptamethines derivatives permitted the fine tuning of their optical properties upon a large spectral region and evidenced a new bis-dipolar electronic structure. Within this dye family, keto heptamethine derivatives has been tested in bio-imaging experiments (living cells and brain) using non-linear microscopy. Finally, the elaboration of original unsymmetrical heptamethines is detailed in the last chapter. These chromophores revealed ideal second order NLO properties for applications in electro-optic modulation

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An, Dechang. "Electro-optic polymer-based monolithic waveguide devices with multi-functions of amplification switching and modulation." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035933.

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Gillespie, William U. "Design and experimental evaluation of an electro-optical, sigma-delta modulator for wideband digital antennas." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA386636.

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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, Dec. 2000.
Thesis advisors, Phillip E. Pace, John P. Powers. Includes bibliographical references (p. 91-92). Alo available online.

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22

Pasquali, González Elisa Co (Elisa Carolina) 1975. "Wideband optical frequency comb generator using a phase velocity-matched lithium tantalate electro-optic modulator." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47719.

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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.
Includes bibliographical references (leaves 74-75).
A wideband optical frequency comb generator can be built using an electro-optic modulator that is driven at a frequency of several GHz and that is enclosed in an optical cavity. When light is circulated within the optical cavity, multiple passes through the modulator produce a spectrum centered at the carrier frequency with hundreds of sidebands spaced at the modulation frequency, with a comb span limited only by the material dispersion of the modulator. We present the design, construction, and testing of an optical frequency comb generator using lithium tantalate as a modulator substrate.
by Elisa C. Pasquali González.
M.Eng.

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23

Chopard, Adrien. "Demonstration of a free-space optical communication link in the 10-meter range using electro-absorption modulator arrays." Thesis, KTH, Tillämpad fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202613.

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Gan, Haiyong. "Electro-optic Polymer Based Fabry-Perot Interferometer Devices for Optoelectronic Applications." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195839.

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Fabry-Perot interferometer (FPI) devices are designed based on the electro-optic (EO) activities of nonlinear optical (NLO) polymer materials for tunable optical filters (TOFs) and spatial light modulators (SLMs). The performance of the EO polymer based FPI devices is theoretically modeled with first order approximation on the FPI cavity interface phase dispersion. NLO materials including TCBD coupled hybrid sol-gel, AJL8/amorphous polycarbonate (APC), and AJLS102/APC are incorporated in FPI structures with distributed Bragg reflector mirrors and transparent conducting oxide electrodes for TOFs. High finesse (over 200), low drive voltage (10 dB isolation ratio with 5 V), and fast settling time (about sub-millisecond) are achieved. The physical origin of the large tunabilities is explored and the contributions from EO effect and inverse piezoelectric effect are analyzed. EO polymer SWOHF3ME/APC is employed in FPI devices with simplified structures for SLMs. Modulation beyond megahertz level is achieved with constant modulation ratio from DC frequency to high operation speed. The operation speed can be potentially over gigahertz with improved device and drive circuit design. When the EO polymer based SLM is configured to work at near the resonance band of the NLO material, the spectral tunability is increased due to resonance enhanced EO activity and the SLM performance is significantly improved. The EO polymer based FPI devices can be further optimized and are promising candidates for many optoelectronic applications.

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Poggi, Daniele. "Physical modeling of optical modulators for optical link analysis : Optical link analysis in silicon photonics technologies." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-247887.

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According to the 2018 Ethernet Roadmap projections, the requirements for high speed links keep increasing every year, always keeping an eye on the energy per bit consumption of the communication system. The Ethernet requirements are estimated to reach 1Tbps by 2022-2025. Optical links are one of the most concrete solutions to satisfy bandwidth requirements at low energy consumption. An optical link is a communication system that consists of a single end-to-end optical circuit. In contrast with vertical-cavity surface-emitting laser (VCSEL) technology, which is based on a direct laser modulation, silicon photonics technology (SPT) is based on indirect modulation. In order to perform the modulation, electro-optical modulators are needed in the optical link system for electrically modulating the optical power.This master thesis, developed at imec, will present the modeling of two different technologies of optical modulators: Silicon Ring Modulator and the Franz-Keldysh ElectroAbsorption Modulator. The work was initiated, since there were no available models of these devices in the actual framework for link analysis. First a preliminary study of the physical principles of the two devices was performed, in order to build the Matlab models. Then, these models were fitted with measurements, in order to adjust them to real-life behavior. After having obtained two working models of the two modulators, an alreadyexisting framework was used, to compare the energy consumption per bit in the optical link. However, the results obtained with the simulation didn’t highlight a technology to be preferred to the other.
Enligt prognoserna från Ethernet Roadmap 2018 fortsätter kraven på höghastighetslänkar att öka varje år och håller alltid ett öga på kommunikationssystemets energi konsumtion per bit. Ethernet-kraven beräknas nå 1Tbps 2022-2025.Optiska länkar är en av de mest konkreta lösningarna för att tillgodose bandbreddskrav vid låg energiförbrukning. En optisk länk är ett kommunikationssystem som utgör en punkt till punkt förbunden optisk krets. I motsats till teknik som utnyttjar den vertikala kavitetsytemitterande lasern (VCSEL), som bygger på en direkt lasermodulering, baseras kisel fotonikteknik (SPT) på indirekt modulering. För att utföra en modulering behövs elektrooptiska modulatorer i det optiska länksystemet för att elektriskt modulera den optiska effekten.Denna masteruppsats, utvecklad vid imec, kommer att presentera modelleringen av två olika teknologier av optiska modulatorer: Silicon Ring Modulatorn och Franz-Keldysh Electro Absorption Modulator. Arbetet, genomfördes eftersom det inte fanns några tillgängliga modeller av dessa enheter i själva ramverket för länkanalys. För det första genomfördes en preliminär studie av de två enheternas fysikaliska principer för att bygga Matlab-modellerna. Sedan jämfördes dessa modeller med mätningar för att anpassa dem till verkligt beteende. Efter att ha fått två arbetsmodeller av de två modulatorerna användes ett redan existerande ramverk för att jämföra energikonsumtionen per bit i den optiska länken. De resultat som erhölls med simuleringen indikerade emellertid inte någon teknik som skulle föredras framför den andra.

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Wang, Shengjia [Verfasser], Alexander W. [Akademischer Betreuer] Koch, Alexander W. [Gutachter] Koch, and Bloise Felix José [Gutachter] Salazar. "Dual Transverse Electro-Optic Modulator in Optical Interferometric Systems / Shengjia Wang ; Gutachter: Alexander W. Koch, Felix José Salazar Bloise ; Betreuer: Alexander W. Koch." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/1204200262/34.

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Abel, Stefan. "Dispositifs électro-optiques à base de titanate de baryum épitaxié sur silicium pour la photonique intégrée." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT004/document.

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En premier lieu, des couches minces épitaxiales ont été obtenues sur des substrats de silicium grâce à l’utilisation de l’épitaxie par jets moléculaire et de couches tampons de titanate de strontium SrTiO3. Une technique de croissance par co-déposition a été développée de manière à obtenir un rapport Ba:Ti proche de la stoechiométrie, et ce afin d’éviter la formation de défauts cristallins dans la couche de BaTiO3. Le matériau déposé cristallise dans une structure de symétrie quadratique, ce qui est unpré-requis pour l’obtention de propriétés électro-optiques. De plus, selon les conditions de croissance, l’axe c de la maille élémentaire quadratique a pu être ajusté de manière à être aligné parallèlement ou perpendiculairement à la surface du substrat. L’utilisation d’une mince couche tampon de nucléation a également permis de croitre des films mincesBaTiO3 épitaxiées par pulvérisation, technique largement répandue en milieu industriel.Un coefficient de Pockels élevé a par la suite été obtenu sur de tellescouches épitaxiées. La valeur mesurée de 148pmV est clairement supérieure aux valeurs admises dans la littérature pour d’autres matériaux nonlinéairestels que le niobate de lithium, pour lequel un coefficient de31pmV est rapporté. La méthode de caractérisation électro-optique développée à cette occasion révèle également le caractère ferroélectrique des couches de BaTiO3, observé pour la première fois dans de tels matériaux épitaxiés sur silicium.Finalement, ces couches minces électro-optiquement actives ont été intégrées dans des dispositifs photoniques sur silicium. Dans cette optique,une structure de guide d’onde à fente a été utilisée en insérant 50nm deBaTiO3 entre deux couches de silicium. Dans ce type de structure, le confine mentoptique est 5 fois supérieur à celui obtenu pour des guides d’onde en silicium avec une gaine à base de BaTiO3. Des guides d’ondes rectilignesont tout d’abord été fabriqués, pour lesquels des pertes optiques del’ordre de 50−100 dB/cm ont été mesurées. Par la suite, des composants passifs fonctionnels ont été fabriqués, tels que des interféromètres typeMach-Zehnder, des résonateurs circulaires et des coupleurs. Finalement,la fonctionnalité de composants actifs a été démontrée pour la première fois, en se basant notamment sur des résonateurs ayant un facteur de qualité Q d’environ 5000, et pour lequel la résonance varie en fonction du champ électrique transverse. L’origine physique de cette variation n’a cependant pas pu être expliquée sur la seule base de l’effet Pockels. Cette thèse démontre que l’utilisation de nouveaux matériaux électro optiquement actifs au coeur de dispositifs photoniques sur silicium créede nouvelles opportunités pour la conception et l’ingénierie de circuitsphotoniques. L’intégration d’oxydes tels que barium titanate permet d’envisager de nouveaux concepts de dispositifs pour ajuster, moduler ou commuter la lumière au sein de circuits photoniques denses. De nouveaux défis et perspectives s’ouvrent également aux scientifiques pour modifier artificiellement les propriétés électro-optiques de ces matériaux, que ce soit par contrainte, dopage ou par l’ingénierie de multicouches. De telles avancées pourront sans aucun doute fortement améliorer les performances des dispositifs
A novel concept of utilizing electro-optical active oxides in silicon photonic devices is developed and realized in the frame of this thesis. The integration of such oxides extends the silicon photonics platform by non-linear materials, which can be used for ultra-fast switching or low-power tuning applications. Barium titanate is used as active material as it shows one of the strongest Pockels coefficients among all oxides. Three major goals are achieved throughout this work: First, thin films of BaTiO3 are epitaxially grown on silicon substrates via molecular beam epitaxy (MBE) using thin SrTiO3 buffer layers. A shuttered co-deposition growth technique is developed in order to minimize the formation of defects in the BaTiO3 films by achieving a 1:1 stoichiometry between barium and titanium. The layers show a tetragonal symmetry and are therefore well-suited for electro-optical applications. The orientation of the long c -axis of the BaTiO3 crystal can be tuned to point perpendicular or parallel to the film surface, depending on the growth conditions. In addition, thin MBE-grown seed layers are combined with rf-sputter deposition. With this hybrid growth approach, rather thick ( > 100 nm), epitaxial BaTiO3 layers on silicon substrates are obtained with a commercially available, wide spread deposition technique. As a second goal, a strong Pockels coefficient of reff = 148 pm/V is determined in the epitaxial BaTiO3 films. This first experimental result on the electro-optical activity of BaTiO3 layers on silicon shows a clear enhancement compared to alternative non-linear materials such as lithium niobate with reff = 31 pm/V. By means of the electro-optical characterization method, also the presence of ferroelectricity in the films is demonstrated. Third, the electro-optical active BaTiO3 layers are embedded into silicon photonic devices. For this purpose, a horizontal slot-waveguide structure with a ~50 nm-thick BaTiO3 film sandwiched between two silicon layers is designed. With this design, the optical confinement in the active BaTiO3 layer is enhanced by a factor of 5 compared to Si-waveguide structures with a standard cross section and BaTiO3 as cladding. Straight BaTiO3 slot-waveguides with propagation losses of 50 − 100 dB/cm as well as functional passive devices such as Mach-Zehnder-interferometers, couplers, and ring resonators are experimentally realized. Additionally, first active ring resonators with Q-factors of Q~5000 are fabricated. The physical origin of the observed resonance shift as a function of the applied bias voltage, however, can not be conclusively clarified in the present work. The combination of high-quality, functional BaTiO3 layers with silicon photonic devices as demonstrated in this thesis offers new opportunities by extending the design palette for engineering photonic circuits with the class of electro-opticalactive materials. The integration of oxides such as BaTiO3 enables novel device concepts for tuning, switching, and modulating light in extremely dense photonic circuits. The integration also opens exciting challenges for material scientists to tailor the electro-optical properties of those oxides by strain engineering or fabrication of superlattice structures, which could ultimately lead to another boost of their electro-optical properties

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28

Lu, Xuejun. "High performance thermo-optic switch and electro-optic modulator based on polymeric multi-mode waveguides with high device packing density for optical network applications." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3034934.

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29

Stolz, Arnaud. "Conception, fabrication et caractérisation d'un modulateur optique à commande plasmonique sur nitrure de gallium à une longueur d'onde de 1,55 micron." Phd thesis, Université de Valenciennes et du Hainaut-Cambresis, 2011. http://tel.archives-ouvertes.fr/tel-00677475.

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Les futurs modulateurs optiques doivent satisfaire à des exigences auxquelles les modulateurs électro-optiques actuels ne peuvent plus répondre (tension de commande et dimensionnement faible, fonctionnement dans la gamme 0-40GHz à faibles pertes). Il devient alors nécessaire d'envisager de nouveaux moyens de réaliser une modulation rapide à faible consommation. Ce travail s'inscrit au sein d'un projet amont de la DGA, afin d'évaluer le gain potentiel de la plasmonique sur semiconducteurs pour la modulation optique. Nous avons d'abord sélectionné des couches de GaN sur saphir avec d'excellentes propriétés optiques et des pertes de propagation de l'ordre de 0,6dB/cm. Ensuite, nous avons montré la génération d'une résonance plasmonique à l'interface Au/GaN. Un travail d'optimisation a été réalisé en vue de rendre sa modulation efficace par variation de l'indice du GaN. Plusieurs dispositifs de démonstration ont été fabriqués en salle blanche puis caractérisés. Si les résultats optiques obtenus ont montré un effet de variation d'indice nouveau jusqu'à Δn=10-2 pour plusieurs dizaines de volt, les pertes RF de propagation se sont révélées élevées, proches de 16dB/cm à 20GHz. En parallèle, une structure à effet d'électro-absorption utilisant un multipuits quantique sur InP a été conçue et caractérisée par couplage par prisme et a montré des variations d'indice de l'ordre de 2×10-3 à 2,5V. Ces travaux de thèse, précurseurs dans ce domaine au sein du laboratoire, vont permettre d'orienter les recherches futures vers de nouveaux matériaux pour l'optoélectronique, mais aussi de mettre en exergue les points durs de la plasmonique pour la modulation optique sur semiconducteurs.

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30

Tang, Yongbo. "Study on electroabsorption modulators and grating couplers for optical interconnects." Doctoral thesis, KTH, Mikroelektronik och tillämpad fysik, MAP, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24178.

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Decades of efforts have pushed the replacement of electrical interconnects by optical links to the interconnects between computers, racks and circuit boards. It may be expected that optical solutions will further be used for inter-chip and intra-chip interconnects with potential benefits in bandwidth, capacity, delay, power consumption and crosstalk. Silicon integration is emerging to be the best candidate nowadays due to not only the dominant status of silicon in microelectronics but also the great advantages brought to the photonic integrated circuits (PICs). Regarding the recent breakthroughs concerning active devices on silicon substrate, the question left is no longer the feasibility of the optical interconnects based on silicon but the competitiveness of the silicon device compared with other alternatives. This thesis focuses on the study of two key components for the optical interconnects, both especially designed and fabricated for silicon platform. One is a high speed electroabsorption modulator (EAM), realized by transferring an InP-based segmented design to the hybrid silicon evanescent platform. The purpose here is to increase the speed of the silicon PICs to over 50 Gb/s or more. The other one is a high performance grating coupler, with the purpose to improve the optical interface between the silicon PICs and the outside fiber-based communication system. An general approach based on the transmission line analysis has been developed to evaluate the modulation response of an EAM with a lumped, traveling-wave, segmented or capacitively-loaded configuration. A genetic algorithm is used to optimize its configuration. This method has been applied to the design of the EAMs on hybrid silicon evanescent platform. Based on the comparison of various electrode design, segmented configuration is adopted for the target of a bandwidth over 40 GHz with as low as possible voltage and high extinction ratio. In addition to the common periodic analysis, the grating coupler is analyzed by the antenna theory assisted with an improved volume-current method, where the directionality of a grating coupler can be obtained analytically. In order to improve the performance of the grating coupler, a direct way is to address its shortcoming by e.g. increasing the coupling efficiency. For this reason, a nonuniform grating coupler with apodized grooves has been developed with a coupling efficiency of 64%, nearly a double of a standard one. Another way is to add more functionalities to the grating coupler. To do this, a polarization beam splitter (PBS) based on a bidirectional grating coupler has been proposed and experimentally demonstrated. An extinction ratio of around -20 dB, as well as a maximum coupling efficiency of over 50% for both polarizations, is achieved by such a PBS with a Bragg reflector underneath.
QC 20100906

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31

Adams, Mitchell Robert. "Dual-Axis Acousto-Optic/Electro-Optic Deflectors in Lithium Niobate for Full-Parallax Holographic Video Displays." BYU ScholarsArchive, 2021. https://scholarsarchive.byu.edu/etd/9159.

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A major limitation of acousto-optic (AO) leaky-mode modulator based holographic displays is their inability to present full-parallax. We propose that full-parallax capabilities can be bestowed on these displays by integrating an electro-optic (EO) phased array into the architecture. We validated this concept by rendering computational models and by fabricating and testing a basic two-axis AO/EO deflector prototype in lithium niobate. This was, to our knowledge, the first instantiation of an integrated, hybrid AO/EO deflector. The prototype had a 6° deflection range along the AO-axis, and a 3° deflection range along the EO-axis. A series of models provide us with a clear path forward for optimizing this deflector. They suggest that an AO/EO modulator with an EO deflection range of 24.5° and that requires less than 7.5 V can be fabricated within the limitations of standard photolithography.

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32

Ngoho, Moungoho Stéphane Samuel. "Contribution à la conception de modules hyperfréquences et optoélectroniques intégrés pour des systèmes optiques à très haut débit." Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0042.

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L’augmentation des capacités des systèmes de télécommunications optiques passe par le développement des dispositifs optoélectroniques innovants et des technologies clés à hautes performances. Ces dispositifs sont sujets à une forte intégration des composants et les technologies déployées mettent en œuvre des fonctions complexes (PDM – QPSK, PDM – 16 QAM, etc.). Il est donc nécessaire avant toute réalisation d’étudier le comportement électromagnétique de ces composants afin d’envisager des performances en haute fréquence et une bonne intégrité du signal contenant l’information dans la chaîne de transmission. Ainsi à travers une modélisation EM – circuit le comportement global d’un modulateur à plusieurs niveaux de phase, basé sur la déplétion de porteurs dans une jonction PN, est étudié et analysé. Le modulateur est dans un premier temps représenté par un modèle prenant en compte la jonction. Cette dernière est modélisée par sa résistance et sa capacité équivalentes. Ensuite le packaging du modulateur avec son circuit d’entrée pour les signaux RF et son circuit de sortie pour l’adaptation de charges en sortie est réalisé et optimisé. Une modélisation EM a également permis de concevoir le circuit d’entrée d’un multiplexeur intégré à un Convertisseur Numérique – Analogique 3 bits, destiné à mettre œuvre une modulation PDM – 64 QAM dans un système optique. Les résultats obtenus respectent les spécifications industrielles et permettent de d’envisager le fonctionnement en haute fréquence des dispositifs intégrés
The increase of the capacities of optical telecommunications systems goes through the development of innovative optoelectronics devices and key technologies with high performances. These devices are subjects to high components integration and the deployed technologies implement complex functions (PDM - QPSK, PDM - 16 QAM etc.). Therefore, it is necessary before any realization to study the electromagnetic behavior of these components in order to predict good performances at high frequency and signal integrity in the transmission chain. Thus, through an EM - circuit modeling, the overall behavior of an electro-optical multilevel modulator based on carrier depletion in a PN junction has been studied and analyzed. The modulator is firstly represented by a model taking in account the junction. The junction is modeled by her equivalents resistance and capacity. Subsequently, the packaging of the modulator with the input and out circuit is realized and optimized. The EM modeling has also helped to design the input circuit of an integrated multiplexer to a 3 bits digital - analog converter for an optical system. The obtained results meet the industry specifications and allow predicting good performances in high frequency for the integrated devices

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Mhaouech, Imed. "Étude du transport de charges dans le niobate de lithium massif et réalisation de fonctions électro-optiques dans le niobate de lithium périodiquement polarisé." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0032/document.

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Le premier volet de cette thèse est consacré à la modélisation des phénomènes de transport dans le LN. Partant d'une analyse critique des modèles de bande usuels, nous montrons leur inadéquation dans le cas du LN et nous proposons un modèle de saut basé sur la théorie des petits polarons. Nous étudions d'abord par simulation Monte-Carlo la décroissance d'une population de polarons liés NbLi4+ relaxant vers des pièges profonds FeLi3+. Nous montrons que les pièges FeLi3+ ont des rayons effectifs particulièrement grands, rayons qui augmentent encore à température décroissante, et limitent considérablement les longueurs de diffusion des polarons. Les résultats de simulations sont ensuite confrontés aux résultats expérimentaux obtenus par différentes techniques ; Absorption photo-induite, Raman, Enregistrement holographique et Pompe-sonde. Le deuxième volet de cette thèse est consacré aux applications électro-optiques dans le LN périodiquement polarisé (PPLN). Sous l’effet d’une tension électrique, l’indice de réfraction du PPLN est périodiquement diminué et augmenté, formant ainsi un réseau d’indice activable électriquement. Un premier composant utilisant l’effet électro-optique dans du PPLN a été développé et démontré expérimentalement. Dans ce composant, la lumière est défléchie sous l’effet de la tension électrique par le réseau d’indice. Ce déflecteur de Bragg atteint une efficacité de diffraction proche de 100% avec une faible tension de commande de l’ordre de 5 V. Un deuxième composant a également été proposé, où la lumière se propage perpendiculairement aux parois de domaines du PPLN. Dans cette configuration un réflecteur de Bragg électro-optique peut être réalisé
The first part of this thesis is devoted to the modeling of transport phenomena in the LN. From a critical analysis of the usual band models, we show their inadequacy in the case of LN and we propose a hopping model based on the theory of small polarons. We first study by Monte-Carlo simulation the population decay of bound polarons NbLi4+ in deep traps FeLi3+. We show that the traps (FeLi3+) have particularly large effective radii, which increase further at decreasing temperature, and considerably limit the diffusion lengths of the polarons. The results of simulations are then compared with experimental results obtained by different techniques; Light-induced absorption, Raman, Holographic storage and Pump-Probe. The second part of this thesis is devoted to electro-optical applications in the periodically poled LN (PPLN). Under the effect of an electrical voltage, the refractive index of the PPLN is periodically decreased and increased, thus forming an electrically activatable index grating. A first component using the electro-optical effect in PPLN has been developed and demonstrated experimentally. In this component, the light is deflected under the effect of the electrical voltage by the index grating. This Bragg deflector achieves a diffraction efficiency of close to 100% with a low drive voltage of the order of 5 V. A second component has also been proposed, where light propagates perpendicularly to the domain walls of the PPLN. In this configuration an electro-optic Bragg reflector can be realized

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34

Sato, Sandra Sayuri. "Simulação multifísica utilizando método dos elementos finitos auxiliando interativamente a fabricação de moduladores eletro-ópticos em substratos de Bi4Ge3O12." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-21072016-091619/.

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Este trabalho apresenta um método desenvolvido pela autora para, através de simulações multifísicas pelo Método dos Elementos Finitos (MEF), servir como ferramenta de apoio ao projeto e fabricação de guias de onda e moduladores eletro-ópticos em óptica integrada, além de possibilitar a análise da performance de moduladores eletro-ópticos. A técnica adotada para a fabricação dos guias de onda ópticos foi a de tensão mecânica. Os parâmetros de geometria (espessura do filme e larguras das trincheiras) e de temperatura de deposição do filme são definidos nas simulações e utilizados no processo de fabricação de guias de ondas em óptica integrada, que servem de base para a fabricação de moduladores eletro-ópticos em substrato cristalino de retículo cúbico. As trincheiras dos guias de onda do tipo canal são construídas em Germanato de Bismuto (BGO - Bi4Ge3O12), a partir da deposição sobre o substrato de um filme fino indutor de tensão mecânica (stress) Nitreto de Silício (Si3N4) e definidas pelos processos de litografia óptica e corrosão seletiva por plasma. Os moduladores são obtidos através da deposição dos eletrodos de alumínio sobre o filme, seguida de Si3N4 dos processos de litografia óptica e corrosão, obtendo-se eletrodos. O processo iterativo proposto inicia-se com os resultados das simulações, em que são definidos os parâmetros de fabricação do filme, da trincheira e dos eletrodos. Após a fabricação desses elementos, o componente é caracterizado e são medidos os parâmetros reais filme e do substrato. Esses valores são realimentados nas simulações para refinar o projeto do componente. O trabalho, além de apresentar todos os passos do processo interativo de simulações, projeto, fabricação e caracterização do componente desejado, indica as dificuldades encontradas na implementação do processo e as atividades futuras a serem desenvolvidas para o aperfeiçoamento do mesmo.
This work presents a method developed by the author to support the project and fabrication of integrated optic waveguides and electro-optic modulators by means of Finite Element Method (FEM) multiphysics simulations, also enabling the electro-optic modulators performance analysis. The technique used for fabricating the optical waveguides was the thermally induced residual stress (ISS). The geometry parameters (film thicknesses and trenches widths) and the film deposition temperature are obtained in the simulations and subsequently used in the integrated optical waveguides fabrication process, which serve as a basic building block for the electrooptic modulators on crystalline cubic lattice substrate. The channel waveguide trenches are built on Bismuth Germanate (BGO Bi4Ge3O12) by depositing a Silicon Nitride (Si3N4) Stress-inducing thin film, being later defined by optical lithography and plasma etching process. Modulators are obtained depositing aluminum on the Si3N4 film followed by the optical lithography and corrosion process, defining electrodes. The proposed iterative process starts with the simulation results that define the fabrication parameters of the film, trench and electrodes. After the fabrication of these elements, the device is characterized and the actual parameters of the film and substrate are measured. These values are fed back into the simulations to refine the component design. The work besides presenting all the simulation-design-fabrication-characterization iterative process for obtaining the devised device also highlights the difficulties encountered in the implementation process along with suggestions of future activities aiming at improving it.

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35

Fu, Kuang-Yu, and 傅光宇. "Electro-Optical Modulation of the Liquid Crystal Device." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/92320266974190495014.

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碩士
國立彰化師範大學
光電工程技術研究所
92
In this thesis, frequency modulations were demonstrated using a liquid crystal light shutter operated in the electric controlled birefringence mode. When the sinusoidal waves was applied to the LC cell, the output sinusoidal waveforms with double or quadratic frequency of the input signal were generated. Also, the output amplitudes and offsets exhibit periodic oscillations. The applied voltage and the backflow effect contribute to the observed phenomena, and the experimental results were compared and explained qualitatively with the simulation results.

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36

Hsieh, Chih-Wuei, and 謝志威. "Novel Integrated-Optic Surface-Plasmon-Resonance Biosensor by Electro-Optical Modulation." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/2j99te.

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碩士
國立臺北科技大學
光電工程系所
94
In this study, we present a novel integrated-optic surface-plasmon-resonance (SPR) biosensor by electro-optically modulation, which can be used to measure the refractive index of sensing liquid and the concentration of biochemical material. Its device structure consists of a titanium-diffused waveguide, one pair of electrode, and a sensing region. Two kinds of excited layer of surface plasmon, gold film and gold nanoparticle on gold film, are adopted in the sensor, respectively. In order to specifically sense the concentration of biochemical material, human-serum-albumin (HSA) bonded on the excited layer of surface plasmon by the self-assembling method is used as the biolayer and can be used to real-time sense the concentration of beta-blocker, which is a kind of medicine for heart disease. During the sensor measurement, the SPR phase can be tuned by electro-optic effect in lithium niobate and the property of the sensing material can be detected by the relation between the phase and the voltage. Because of the surface effect of nano particles, gold nano particles are used on the biosensor to increase the surface coverage of human-serum-albumin. In comparison with the conventional SPR sensor, the proposed SPR sensor has many advantages, such as: high accuracy, high sensitivity, and easy operation. The integration of the proposed integrated-optic SPR biosensor with other functional devices in one single lithium niobate chip will facilitate the processing of optical sensing signal to further reduce the system volume and to achieve high-throughput screening.

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37

Li, Tsung-Hsun, and 李宗勳. "Analysis on electro-optical modulation of liquid crystal on a metallic grating structure." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/41295144238068839173.

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碩士
國立中山大學
光電工程學系研究所
104
Surface plasmon resonance (SPR) is sensitive to surface structure, metal thickness or refraction index of medium layer. Liquid crystal is anisotropic, and optically, the refraction index of light is related to its direction and polarization. In this research, the birefringent nematic liquid crystal (NLC) with uniaxial crystal structure, E7, was injected to a liquid crystal cell with metallic gratings, and placed on a prism with Kretschmann structure. From the characteristics of electro-optical modulation of liquid crystal, E7 was used to serve as the switch which can couple surface plasma wave. Pumping light source was controlled to be coupled or un-coupled by changing the refraction index of liquid crystal, and SPR mode effect modulated by liquid metal would be reached.

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38

Ho, Po-Ching, and 何柏慶. "Localized Surface-Plasmon-Resonance Biosensing System by Electro-Optical Modulation in the ATR Configuration." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/m78v64.

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碩士
國立臺北科技大學
光電工程系研究所
97
In this dissertation, we present an electro-optically modulated localized surface plasmon resonance biosensing system in the attenuated-total-reflection configuration, which can be used to measure the concentration of biochemical material. The sensing chip consists of a sensing region and one pair of electrodes on the ridge structure. When the voltage is applied on the electrodes, the electric field produced in lithium niobate electro-optically modulates the refraction index and changes the wave vector of the incidence lightwave. In this study, we use two kinds of measurement configurations, including optical intensity and phase shift configuration. Excited layer of surface plasmon formed by gold nanoparticle on gold film is adopted in the sensor. Human serum albumin (HSA) produced by the self-assembling method is used as the sensing layer to real-time sense the concentration of beta-blocker, which is a kind of medicine for heart disease. During the sensing measurement, the concentration of beta-blocker can be determined by the relation between the reflection intensity (or the phase shift) and the voltage. In comparison with the conventional SPR sensing, the proposed SPR sensing system has many advantages, such as: high accuracy, high sensitivity, and easy operation. In the future application, the presented biosensing system can be utilized to measure the interaction between HSA and medicines molecule for understanding the interaction mechanism of medicine in the human body.

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39

Roth, Matthias. "Contributions to the design of Fourier-optical modulation systems based on micro-opto-electro-mechanical tilt-mirror arrays." 2020. https://tud.qucosa.de/id/qucosa%3A72525.

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Spatial Light Modulators (SLMs) based on Micro-Opto-Electro-Mechanical Systems (MOEMS) are increasingly being used in various fields of optics and enable novel functionalities. The technology features frame rates from a few kHz to the MHz range as well as resolutions in the megapixel range. The field continues to make rapid progress, but technological advancements are always associated with high expenditure. Against this background, this dissertation addresses the question: What contribution can optical system design make to the further development of MOEMS-SLM-based modulation? A lens is a simple example of an optical system. This dissertation deals with system design based on Fourier optics in which the wave properties of light are exploited. On this basis, arrays of micromirrors can modulate light properties in a spatially resolved manner. For example, tilt-mirrors can control the intensity distribution in an image plane. In this dissertation variations of the aperture required for this are investigated. In addition to known absorbing apertures, phase filters in particular are investigated, which apply a spatially distributed delay effect to the light wave. This dissertation proposes the combination of MOEMS-SLMs with static, pixelated elements in the same system. These may be pixelated phase masks, also known as diffractive optical elements (DOEs). Analogously, pixelated polarizer arrays and absorbing photomasks exist. The combination of SLMs and static elements allows new degrees of freedom in system design. This thesis proposes new modulation systems based on MOEMS tilt-mirror SLMs. These systems use analog tilt-mirror arrays for the simultaneous modulation of intensity and phase as well as intensity and polarization. The proposed systems thus open up new possibilities for MOEMS-based spatial light modulation. Their properties are validated and investigated by numerical simulations. System properties and limitations are derived from these near and far field simulations. This dissertation shows that the modulation of different MOEMS-SLM types can be fundamentally changed by system design. Piston mirror arrays are classically used for phase modulation and tilt-mirror arrays for intensity modulation. This thesis proposes the use of subpixel phase structures. Their use approximately provides tilt-mirrors with the phase-modulating effect of piston-mirrors. In order to achieve this, a new optimization method is presented. Piston-mirror arrays are available only to a limited extent. By contrast, tilt-mirror arrays are well established. In combination with subpixel phase features, tilt-mirrors may replace piston-mirrors in some applications. These and other challenges of MOEMS-SLM technology can be adequately addressed on the basis of system design.
Räumliche Lichtmodulatoren (Spatial Light Modulators, SLMs) auf Basis von Mikro-Opto-Elektro-Mechanischen Systemen (MOEMS) finden zunehmend Anwendung in verschiedensten Teilgebieten der Optik und ermöglichen neuartige Funktionalitäten. Die Technik ermöglicht Frameraten von einigen kHz bis in den MHz-Bereich sowie Auflösungen bis in den Megapixelbereich. Der Fachbereich macht nach wie vor rasche Fortschritte, technologische Weiterentwicklungen sind aber stets mit hohem Aufwand verbunden. Vor diesem Hintergrund widmet sich diese Arbeit der Frage: Welchen Beitrag kann optisches Systemdesign zur Weiterentwicklung der MOEMS-SLM-basierten Modulation leisten? Bereits eine Linse stellt ein Beispiel für ein optisches System dar. Diese Dissertation beschäftigt sich mit Systemdesign auf Basis der Fourier-Optik, bei der die Welleneigenschaften des Lichts genutzt werden. Auf dieser Basis können Arrays von Mikrospiegeln die flächige Verteilung von Licht einstellen. Beispielsweise können Kippspiegel die Intensitätsverteilung in einer Bildebene steuern. In dieser Dissertation werden Variationen der dafür nötigen Apertur untersucht. Neben bekannten absorbierenden Blenden werden insbesondere Phasenfilter untersucht, welche eine flächig verteilte Verzögerungswirkung auf die Lichtwelle aufbringen. Diese Dissertation schlägt die Kombination von MOEMS-SLMs mit statischen, pixelierten Elementen im selben System vor. Hierbei kann es sich um pixelierte Phasenmasken handeln, auch bekannt als diffraktive optische Elemente (DOEs). Analog existieren pixelierte Polarisatorarrays und absorbierende Fotomasken. Die Kombination von SLMs und statischen Elementen ermöglicht neue Freiheiten im Systemdesign. Diese Arbeit schlägt neue Modulationssysteme auf Basis von MOEMS-Kippspiegel-SLMs vor. Diese Systeme nutzen analoge Kippspiegelarrays für die simultane Modulation von Intensität und Phase sowie von Intensität und Polarisation. Die vorgeschlagenen Systeme eröffnen damit neue Möglichkeiten für die MOEMS-basierte Flächenlichtmodulation. Ihre Eigenschaften werden mithilfe von numerischen Simulationen validiert und untersucht. Aus diesen Nah- und Fernfeldsimulationen werden Systemeigenschaften und Limitierungen abgeleitet. Es wird in dieser Arbeit gezeigt, dass die Modulation verschiedener MOEMS-SLM-Typen auf Basis des Systementwurfs fundamental verändert werden kann. Senkspiegelarrays werden klassischerweise zur Modulation der Phase eingesetzt und Kippspiegelarrays zur Modulation der Intensität. Diese Arbeit schlägt die Nutzung von Subpixel-Phasenstrukturen vor. Diese verleihen Kippspiegeln näherungsweise die phasenmodulierende Wirkung von Senkspiegeln. Um dies zu erreichen, wird ein neuartiges Optimierungsverfahren vorgestellt. Senkspiegelarrays sind nur in geringem Umfang verfügbar. Im Gegensatz dazu sind Kippspiegelarrays gut etabliert. In Kombination mit Subpixel-Phasenstrukturen könnten Kippspiegel in einigen Anwendungen Senkspiegel ersetzen. Diese und andere Herausforderungen der MOEMS-SLM-Technologie lassen sich auf der Grundlage des Systemdesigns adäquat adressieren.

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40

Lee, Kun-Yu, and 李堃毓. "Asymmetric Ge/SiGe Quantum Well Applied for Optical Electro Absorption Modulator." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/32721258802910025720.

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碩士
國立清華大學
光電工程研究所
100
Optical electroabsorption modulators using quantum confinement Stark effect are important devices in optical commincation. Ge is group IV element that is compatible with Si process. It is possible to integrate Ge/SiGe quantum well devices with integrated circuite. In this thesis, we study the eigen state of carrier and analyze the electroabsorption in an asymmetric quantum well. We find out that if the barrier height of carriers in conduction band and valance band are different, there exists blue shift when electric field is applied. We further suggest a design rule for engineering the blue shift, and with this rule, we demonstrate an example of elctroabsorption modulators with Ge/SiGe asymmetric quantum well.

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41

Lee, Yi-Huan, and 李宜桓. "A Waveguide Electro-Optic Modulator for the Applications of Optical Heterodyne Interferometry." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/51963937677950901197.

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碩士
南台科技大學
光電工程系
98
In this thesis, the applications of the homemade Zn-Indiffused electro-optic modulator (ZIEOM) have been evaluated and applied for optical heterodyne interferometry at visible wavelengths (532nm, 632.8nm, and 670nm). The switching voltages and phase stabilities of the proposed waveguide modulator are further compared with the commercial buck-type modulator (EOM). The results show that the ZIEOM has a lower switching voltage and better phase stability than that of the EOM. Moreover, the ZIEOM can be used to modulate the stable heterodyne light sources for various polarization interferometers at the visible wavelengths. A number of metrology applications including optical temperature sensors and photorefractive measurements have been successfully developed by using the ZIEOM.

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42

Su, Huan-Kuan, and 蘇桓寬. "Fabrication and measurement of asymmetric PN junction silicon microring electro-optical modulator." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/51920429730206810721.

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43

Chen, Ren-Yu, and 陳人郁. "An investigation of Ta2O5 optical waveguide for electro-optical absorption modulator with a thin InOx absorption layer." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/83yt5n.

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碩士
國立中山大學
光電工程學系研究所
106
In the thesis, we fabricated Ta2O5 optical waveguide with a thin InOx layer and investigated the absorption effect of the InOx layer. The Ta2O5 films were prepared using the RF-magnetron sputtering system on silicon substrates with 3-μm thick thermal oxide. The waveguide devices obtained by conventional photolithography to define pattern and dry etching to form the Ta2O5 rib-waveguide. Furthermore, we deposited InOx thin layer upon the Ta2O5 rib to form a thin absorption layer. Finally, the Ta2O5/InOx electro-optical absorption modulator was completed by depositing 1.8-μm SiOx as top cladding using sputtering. The waveguide devices were fabricated by first forming the Ta2O5 core using CHF3 plasma etching. In addition, we deposited InOx thin layer at 15% and 30% O2 partial pressure by sputtering. Contact to the InOx was formed by etching away the SiOx top cladding. Finally, the waveguide devices were forming the back Al contact to Si substrate to complete absorption modulator device. The waveguide and modulator devices were measured by a home-made optical system with 1310nm TOSA (Transmitter Optical Sub-assembly) laser. As a result, we demonstrated the Ta2O5 rib-waveguide that propagation loss and coupling loss at 1310nm were 8.35dB/cm and 3.39dB, respectively. The insertion loss was 12.81dB with 7.3mm long Ta2O5 rib-waveguide. In addition, the propagation loss of the Ta2O5 rib-waveguide with thin InOx absorption layer at 30% oxygen partial pressure was 17.67dB/cm. The propagation loss of 15% O2 partial pressure InOx of the InOx -Ta2O5 rib-waveguide was 23.7dB/cm. At a bias of 10V, the Ta2O5/InOx electro-optical modulator exhibits an excess loss of only 0.25dB. The low absorption loss of the device can be caused by poor electrode structure for biasing.

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44

Guite, Chinkhanlun. "Experimental Studies Of Electron Spin Dynamics In Semiconductors Using A Novel Radio Frequency Detection Technique." Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2458.

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A novel experimental setup has been realized to measure weak magnetic moments which can be modulated at radio frequencies (~1–5 MHz). Using an optimized radio-frequency (RF) pickup coil and lock-in amplifier, an experimental sensitivity of 10 -15 Am2 corresponding to 10 -18 emu has been demonstrated with a one second time constant. The detection limit at room temperature is 9.3 10 -16 Am2/√Hz limited by Johnson noise of the coil. In order to demonstrate the sensitivity of this technique it was used to electrically detect the polarized spins in semiconductors in zero applied magnetic fields. For example in GaAs, the magnetic moment due to a small number (~ 7 x 108) of spin polarized electrons generated by polarization modulated optical radiation was detected. Spin polarization was generated by optical injection using circularly polarized light which is modulated rapidly using an electro-optic cell. The modulated spin polarization generates a weak time-varying magnetic field which is detected by the sensitive radio-frequency coil. Using a radio-frequency lock-in amplifier, clear signals were obtained for bulk GaAs and Ge samples from which an optical spin orientation efficiency of ~ 10–20% could be determined for Ge at 1342 nm excitation wavelength at 127 K. In the presence of a small external magnetic field, the signal decayed according to the Hanle Effect, from which a spin lifetime of 4.6 ± 1.0 ns for electrons in bulk Ge at 127 K was extracted. The spin dynamics in n-Ge was further explored and the temperature dependence of the spin lifetime was plotted for a temperature range of about 90 K to 180 K. The temperature dependence of the optical pumping efficiency was also measured though no quantitative conclusions could be derived. The signals observed for semi-insulating GaAs, n-GaAs, GaSb and CdTe which are direct gap semiconductors are much larger than expected (almost two orders of magnitude). An attempt was made to explain this unexpected behavior of these direct gap semiconductors using the spin hall effect.

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45

Lee, How Chiang, and 李豪強. "Reduction of Nonlinear Distortions and Applications of Optical Bistability with Two-stage Electro-optic Modulator." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/32446854673439840723.

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46

Lam, Alfred Kan Min. "Wide band electro-optic intensity modulator frequency response measurement using optical heterodyne, Down-conversation Technique." Thesis, 2005. http://hdl.handle.net/2429/16552.

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In this thesis a novel system for measuring the frequency responses of electrooptic intensity modulators in the millimeter-wave regime is described. As the frequency responses of modulators increase, wide band, and cost effective methods to measure these responses need to be developed. The system described in this thesis uses optical heterodyning and a wide band photodiode to generate millimeter-waves to drive the device under test (DUT). The need for a wide band microwave sweeper can therefore be eliminated. Moreover, an inexpensive frequency shifter consisting of a Mach-Zehnder modulator and an optical bandpass filter is used to down-convert the output of the DUT to a low microwave frequency at which the output is easily measured. The system measures | S₂₁ | in dBe. The system can measure the frequency responses of different types of electrooptic intensity modulators such as Mach-Zehnder modulators, mode-converter modulators, electro-optic polymer modulators, and should also work for electroabsorption modulators. In this thesis, the frequency response measurement system is described, and mathematical expressions for the optical fields at the output of an electro-optic modulator are developed when the DUT is biased or operated at its maximum, quadrature, and minimum points. High frequency measurements on a 10 Gb/s LiNbO₃ Mach-Zehnder type modulator and a 40 Gb/s GaAs mode-converter type modulator are made. The measurements show close agreement with | S₂₁ | measurements made using vector network analyzers and calibrated wide band photodiodes. In addition, the harmonic rejection feature of our system is described. Our system "rejects" higher order harmonics, due to the non-linearities, generated in the DUT with proper selection of the modulation and the shift frequencies. This feature means that our system can measure the linear frequency response of the DUT even if it is operated, or biased, in a non-linear region.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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47

Du, Plessis Jan Harm. "An all-fibre laser distance measurement system utilising figure-eight fibre lasers with electro-optic amplitude modulation." Thesis, 2010. http://hdl.handle.net/10210/3417.

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M.Ing.
The aim of this project is to research the feasibility of an all-fibre laser distance measurement device that utilises a figure-eight fibre laser (F8L), in the nonlinear amplifying loop mirror (NALM) configuration, as a light source and implements pulse compression to improve the accuracy and signal-to-noise ratio of the system. A figure-eight fibre laser in the NALM configuration for use in a laser distance measurement device is described. The theory of fibre lasers is discussed, including mode-locking and Qswitching, and the characteristics of a NALM loop are analysed. By varying the length of the NALM loop from 500 m to 2000 m or inserting highly nonlinear dispersion shifted fibre, a variety of pulses in the picosecond to nanosecond range can be produced. The lengths of the pulses depend on the length of the NALM loop, the pump power and the setting of the polarisation controllers. The figure-eight fibre laser is pumped with a 980 nm laser diode up to 550 mA, which corresponds to 320 mW. Distance measurements are done with short unmodulated and long modulated pulses. Distance measurement with short unmodulated pulses is discussed only briefly and tested with a simple experiment. The focus of this project is distance measurement with long modulated pulses. A low autocorrelated binary sequence is modulated onto one of the long pulses produced by the figure-eight fibre laser by an electro-optic amplitude modulator. The long pulse gives the proposed system a good signal-to-noise ratio (SNR), while the modulation improves the accuracy. A Barker code of length 13 is proposed as modulation code because of its good autocorrelation properties. The Barker code will improve the accuracy 13-fold, with a corresponding increase in SNR. An electro-optic amplitude modulator is used to implement the modulation. The modulated long pulse is then sent to a target. After reflection, the signal is detected and cross-correlated to obtain the time-of-flight for the pulse. The code generation and cross-correlation are implemented with an FPGA via VHDL programming. The distance to a target can be calculated by knowing the time-of-flight and the speed of light in the propagation medium. In this project the resolution, single-shot precision, accuracy, linearity, repeatability and maximum unambiguous distance of the proposed all-fibre laser distance measurement device are examined.

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48

Shao, Hsiang-Yun, and 邵湘芸. "The Studies for Bidirectional Transmission Systems in ROF-PON Using Electro-Absorption Modulator and Optical Interleaver." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/69779858147934932147.

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碩士
明志科技大學
電機工程系碩士班
102
In recent years, technology gradually innovation, breakthroughs, progress, nowadays the Internet has become an internet of life indispensable, these techniques often require high bandwidth capacity in fiber-optic transmission systems. Radio over Fiber-Passive Optical Network (ROF-PON) is a common technology, can supply bandwidth capacity transmission and has low loss, high security and flexibility of the system, provides users with high-quality and diverse wealth of network services. In order to enable the system to diversify, practical, will change the previous using unidirectional transmission of bidirectional transmission, but in bidirectional transmission system will generate Rayleigh backscattering problem. Changes in the transmission path and modulation scheme can improve the problem of Rayleigh backscattering(RB)。 In the proposed scheme, the studies for bidirectional transmission systems in ROF-PON using Electro-Absorption modulator(EAM) and Optical Interleaver(IL). Transmitter using electro-absorption modulator laser as the light source, interleaver filter the odd and even source through the 25km single mode fiber(SMF) transmission do the test, the even source is downlink wavelength is reused for uplink in BS, through the intensity modulation and phase modulation of different modulation schemes again modulated ,and transmitted toward the central office(CO).

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49

Chang, Chieh-Po, and 張介柏. "Polychromatic Electro-Optical Pattern Recognition System with Liquid Crystal Spatial Light Modulator Based on Color Human Vision Model." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/42763148924604610483.

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Abstract:

碩士
元智大學
光電工程研究所
96
People consider that ATD color model is the most to be close to human eyes. In this thesis, we apply ATD color model to multi-channel nonzero order joint transform correlator and perform pattern recognition. To estimate whether ATD color model is suitable for pattern recognition, we utilize the multi-level quantized reference functions to discuss the effect of pattern recognition. Furthermore, we compare with RGB, which is common used to perform pattern recognition. The terms of estimation contain recognition ability of rotational distortion, brightness performance, effect of multi-level quantized reference functions, noise tolerance ability, recognition ability of realistic background, and relationship between channels and channels. We utilize peak to correlation energy, peak to sidelobe ratio, correlation peak intensity, and mutual correlation coefficient as our performance evaluation parameters. Finally, the results show that ATD color model is suitable for pattern recognition.

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Dissertations / Theses on the topic 'Electro-optical modulation'

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