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Análise de fibras ópticas microestruturadas pelo método da sobre relaxação sucessiva / Analysis of microstructured optical fiber by the successive over relaxation methodDanilo Henrique Spadoti 27 August 2004 (has links)
Neste trabalho é investigada uma nova classe de fibras ópticas, baseada no conceito de cristais fotônicos, denominada fibra microestruturada. Sua geometria particular, com materiais de diferentes índices de refração estruturados de forma periódica, permite uma alta flexibilidade de projeto. Consegue-se, portanto, ajustar, conforme a necessidade, as propriedades de dispersão, área efetiva, perdas por confinamento, entre outras, o que torna estas fibras especialmente úteis para aplicações em comunicações ópticas. Para o estudo das propriedades das fibras microestruturadas foi implementado, em diferenças finitas, o método numérico da sobre relaxação sucessiva - SOR com as três aproximações possíveis para a equação de Helmholtz: escalar, semivetorial e vetorial completa. Adicionalmente, no intuito de melhorar alguns aspectos do formalismo SOR, como precisão e velocidade de convergência, foi proposta a aproximação em diferenças finitas de quarta ordem. / This work investigates a new class of optical fibers based on the photonic crystal concept. The main advantage of these fibers is the flexibility offered by their particular geometry, which is formed by materials of different refractive index periodically arranged in a specific pattern. The dispersion properties of these microstructured optical fibers are analyzed by using the finite difference Successive Over Relaxation (SOR) method, where three different formalisms are implemented under the scalar, semivectorial and full vectorial approximations. Finally, a fourth order approximation for the SOR method is proposed in order to improve the convergence and precision.
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Proposição e estudo de fibras ópticas microestruturadas tipo D: gerenciamento de dispersão e alta birrefringência / Proposal and study of microstructured optical fiber D-type: dispersion management and high birefringenceDanilo Henrique Spadoti 02 October 2008 (has links)
Este trabalho de doutoramento propôs investigar novas configurações geométricas para as fibras ópticas microestruturadas a base de sílica. Aproveitando-se da flexibilidade que sua geometria proporciona, diferentes das fibras ópticas convencionais, foram propostas fibras ópticas microestruturadas com perfil tipo D atuando, especificamente, em duas aplicações distintas: fibras compensadoras de dispersão ou fibras altamente birrefringentes. Para o estudo teórico das fibras ópticas microestruturadas foram utilizados dois métodos numéricos: o método da Sobre-Relaxação Sucessiva (SOR) e o método de Arnoldi Implicitamente Reiniciado (IRAM). Foi necessário implementar o método IRAM para determinar os modos de mais alta ordem presentes em guias de onda multimodos, uma vez que o método SOR fornece apenas a solução para o modo fundamental. Neste contexto, as fibras ópticas microestruturadas com perfil D, propostas e investigadas neste trabalho, demonstraram ser extremamente promissoras para atuar na compensação da dispersão cromática ou no aumento do efeito da birrefringência. Foram projetadas fibras capazes de compensar a dispersão em banda larga, cobrindo as bandas de telecomunicações S, C e L, ou, ainda, fibras com um alto coeficiente de dispersão negativo em torno do comprimento de onda de 1550nm. Adicionalmente, verificou-se também que com as novas configurações propostas foi possível projetar fibras com elevado grau de birrefringência, sendo atrativas no projeto de fibras mantedoras do estado de polarização. / This work proposed to investigate new geometric configurations for the silica microstructured optical fibers. Based on their design flexibility, not usually found in conventional silica fibers, D-shape microstructured optical fibers were designed, specifically, for two different applications: dispersion compensation or high birefringence. For the theoretical analysis two numerical methods were used: the finite difference Successive Over Relaxation (SOR) method, and the Implicitly Restarted Arnoldi Method (IRAM). It was necessary to develop the IRAM method to determine the higher order modes inside the multimodo optical waveguide, since the SOR method is able to yield only the fundamental mode. In this framework, the D-shape microstructured optical fibers, which have been proposed and investigated in this work, proved to be extremely efficient for chromatic dispersion compensation and increasing the birefringent effect. Fibers have been designed in order to compensate the wideband dispersion, covering three entire telecommunication bands, namely: S-, C- and L- bands, simultaneously. Additionally, with these new proposed configurations it is possible to design high birefringent fibers, which are very attractive in polarization maintaining applications.
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Dispositivos baseados no preenchimento de fibras de cristal fotônico por líquidos e materiais nanoestruturados / Devices based on the filling of photonic crystal fibers by liquids and nanostructured materialsSantos, Alexandre Bozolan dos 17 April 2012 (has links)
Esta tese descreve a demonstração experimental de dispositivos baseados em fibras de cristal fotônico (PCFs), que aproveitam a flexibilidade estrutural oferecida pela matriz de capilares que compõe a seção reta da fibra, de forma a preencher estes capilares com líquidos e materiais nanoestruturados. Para o caso de materiais nanoestruturados, uma vez preenchida a fibra, os materiais nela inseridos interagem eficientemente com a luz guiada. Essa arquitetura diferenciada em relação às fibras ópticas convencionais abre novas perspectivas no desenvolvimento de aplicações como óptica não-linear e sensoriamento. PCFs de núcleo líquido, por outro lado, impõe dificuldades para a implementação de dispositivos práticos, devido às altas taxas de evaporação dos líquidos inseridos. Por esta razão, foi desenvolvida uma nova técnica para vedar seletivamente ambas as faces externas do núcleo líquido de uma PCF, utilizando um polímero curável. Estes tampões poliméricos evitam a evaporação, causando um impacto mínimo no guiamento da luz, tornando o dispositivo usável por semanas. Esta nova técnica de vedação foi empregada em um experimento para a geração de supercontínuo em uma PCF com núcleo de água destilada, proporcionando uma estabilidade de pelo menos 1 hora. Combinando líquidos e materiais nanoestruturados, foi também foi desenvolvido um sensor de temperatura baseado no preenchimento do núcleo de uma PCF por uma amostra coloidal de nanopartículas semicondutoras de CdSe/ZnS, dispersas em óleo mineral. O espectro de luminescência destes pontos quânticos coloidais é fortemente dependente da temperatura e os resultados obtidos mostraram que a grande interação entre a luz e o colóide, aliada a geometria da fibra, proporcionando uma sensibilidade ~5,5 vezes maior que a apresentada por uma rede de Bragg escrita em uma fibra óptica padrão, com boa relação sinal-ruído. / This thesis describes the experimental demonstration of devices based on photonic crystal fibers (PCFs). PCFs are optical fibers whose core is surrounded by a regular matrix of holes, which runs longitudinally across its length. This singular configuration allows the insertion of liquids and nanostructured material into the fiber. Nanostructured materials embedded inside the fiber efficiently interact with the guided light, opening up possibilities of novel applications regarding the fields of non-linear optics, as well as optical sensing. On the other hand, liquid-core PCFs suffer from some disadvantages concerning practical device applications, on account of the high evaporation of the inserted liquids. In order to address this issue, we developed a novel technique to selectively seal the external faces of a liquid-core PCF, by using a polymer plug. These polymer plugs avoid evaporation while causing a minimum impact on the light guiding characteristics of the PCF. This novel sealing technique was employed in a supercontinuum generation experiment, by using a PCF whose core was water-filled. A temporal stability of at least one-hour on the resulting spectrum was achieved. Combining the above techniques, we also developed a temperature sensor based on the core-filling of a PCF by a colloidal ensemble of CdSe/ZnS semiconductor nanoparticles dispersed in mineral oil. Those colloidal quantum-dots display a luminescence spectrum which is strongly dependent on temperature and the experimental results indicated that the greater interaction between the guided light and the colloidal sample, provided by the fiber geometry, allowed a sensitivity which is approximately 5.5 times than possible with a conventional Bragg grating, while keeping a satisfactory signal-to-noise ratio.
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Estudo de acopladores de fibra Ãptica tradicional e de cristal fotÃnico e aplicaÃÃes: geraÃÃo de portas lÃgicas e sensor de corrente elÃtrica / Couplers study of traditional fiber optic and photonic crystal and applications: generation of logic gates and electric current sensorAgliberto Melo Bastos 24 July 2015 (has links)
FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / Apresentamos neste trabalho, uma analise numÃrica para obtenÃÃo de portas lÃgicas em acoplador nÃo-linear simÃtrico (NLDC) em fibras de cristal fotÃnico (PCF), que em sua secÃÃo transversal à formada com matriz periÃdica de buracos de ar, operando em pulso de luz ultracurtos na forma de sÃlitons, com duraÃÃo de 100fs (fentosegundos). Foram investigados formatos dos pulsos em modulaÃÃo por amplitude de pulso (PAM), com chaveamento de mudanÃa de amplitude (ASK), com objetivo de obter portas lÃgicas no NLDC-PCF triplo planar simÃtrico. Neste trabalho usamos acopladores duplos de fibra Ãptica na constituiÃÃo de um InterferÃmetro Mach-Zenhder para construir um sensor de corrente, sua funcionalidade à aplicada para investigar a qualidade da corrente alternada, quer seja na geraÃÃo, transmissÃo ou distribuiÃÃo de energia elÃtrica. Como o interferÃmetro de Mach-Zenhder usa um agente mecÃnico, usaremos o mesmo agente para construir o sensor de corrente constituÃdo de um PiezelÃtrico. Ao fazer o comparativo dos dois sensores, podemos destinar sua usabilidade em diferenciados consumidores / In this work, a numerical analysis to obtain gates in coupler symmetrical nonlinear (NLDC) in photonic crystal fibers (PCF), which in cross section is formed with periodic array of air holes, operating in light pulse ultrashort as solitons, lasting 100fs (fentosegundos). The pulses in pulse amplitude modulation formats were investigated (WFP), with amplitude shift keying (ASK), in order to obtain logic gates in the triple NLDC PCF-planar symmetrical. In this paper we use double couplers fiber optic in setting up a Mach-Zenhder Interferometer to build a current sensor, its functionality is applied to investigate the quality alternating current, whether in the generation, transmission or distribution of electricity. Since the interferometer of Mach-Zenhder uses a mechanical agent, agent will use the same for constructing the current sensor constituted of a piezoelectric. In making the comparison of the two sensors, we can allocate its usability in different consumers
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Estudo do desempenho de componentes baseados em fibras Ãpticas especiais: fibras de cristal fotÃnico e de metamateriais e suas aplicaÃÃes em comunicaÃÃes / Study of performance of components based on fiber optics special: photonic crystal fiber and metamaterials and its applications in communicationsAlex Sander Barros Queiroz 26 November 2015 (has links)
nÃo hà / Neste trabalho foi realizado um estudo numÃrico do interferÃmetro de Sagnac baseado em cristais fotÃnicos e de acoplador Ãptico de metamaterial. Na simulaÃÃo do interferÃmetro foram analisados os efeitos da propagaÃÃo da luz, considerando-se a dispersÃo de velocidade de grupo (GVD) e de terceira ordem (TOD), espalhamento Raman intrapulso, auto-inclinaÃÃo (Self-steepening) e auto-modulaÃÃo de fase na equaÃÃo nÃo linear de SchrÃdinger generalizada. No primeiro momento foi realizado o estudo para quatro fatores de razÃo de divisÃo da potÃncia incidente em uma das portas do dispositivo e trÃs dimensÃes para o comprimento do anel do dispositivo. Para caracterizar o desempenho do sistema, foram analisadas as curvas de transmissÃo, taxa de extinÃÃo, crosstalk e fator de compressÃo do pulso transmitido. No segundo momento, foi verificada a performance do chaveamento nÃo-linear para obtenÃÃo de porta lÃgica sob ModulaÃÃo por Amplitude de Pulsos (PAM). Excitando-se as duas portas de entrada do dispositivo com nÃveis lÃgicos "0" e "1", observando o seu comportamento em uma das saÃdas do dispositivo. Inicialmente, variou-se o parÃmetro de ajuste da modulaÃÃo (|ε|), obtendo-se apenas a porta lÃgica OR. E, em uma segunda aplicaÃÃo, manteve-se o parÃmetro da modulaÃÃo fixa e variou-se a fase de uma das portas de entrada, de 0 a 2π rad, encontrando-se portas lÃgicas do tipo OR, AND e XOR. TambÃm foram estudadas as caracterÃsticas de um guia metamaterial que possui a parte real da permissividade elÃtrica e da permeabilidade magnÃtica negativas. Esse guia metamaterial à acoplado com um guia convencional, observando-se as caracterÃsticas de transmissÃo e potÃncia crÃtica desse tipo de acoplador e, comparando-se com um acoplador convencional. Para essa anÃlise foi utilizado um perfil de automodulaÃÃo decrescente linearmente com cinco valores mÃnimo, observando-se um comportamento de histerese. / In this paper we present a numerical study of the Sagnac interferometer based on photonic crystals and optical coupler metamaterial. In the simulation of the interferometer effects of light propagation were analyzed, considering the dispersion of the group velocity (GVD) and third order (TOD), intrapulse Raman scattering, self-slope (self-steepening) and self-modulation phase in the generalized non-linear SchrÃdinger equation. The first time the study was conducted for four power division ratio of factors incident in one of the device ports and three dimensions for the device ring length. To characterize the system performance, were analyzed the transmission curves, extinction ratio, crosstalk and compression factor of the transmitted pulse. In the second moment, the performance of the non-linear switching was observed for obtaining gate under Pulse Amplitude Modulation (PAM). Exciting the two device input ports with logical levels "0" and "1", observing their behavior in one of the device outputs. Initially, the modulation is varied adjustment parameter (| ε |), obtaining only the logical OR gate. And in a second application, the fixed modulation parameter remained and was varied the phase of the input ports 0 to 2π rad, lying type logic gate OR, AND and XOR. The characteristics of a metamaterial guide that has the real part of electrical permittivity and magnetic permeability negatives were also studied. This metamaterial guide is coupled to a conventional guide, observing the transmission characteristics and critical power of this type of coupler and compared with a conventional coupler. For this analysis we used a decreasing automodulation profile linearly with five minimum, observing a hysteresis behavior.
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Modelagem por elementos finitos de dispositivos fotônicos e de RF / Finite element modeling of photonic and RF devicesMalheiros Silveira, Gilliard Nardel, 1980- 16 August 2018 (has links)
Orientador: Hugo Enrique Hernández Figueroa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-16T13:53:46Z (GMT). No. of bitstreams: 1
MalheirosSilveira_GilliardNardel_M.pdf: 3128908 bytes, checksum: 81e325450d7a5eff14ab074c7716b862 (MD5)
Previous issue date: 2010 / Resumo: Esta dissertação aborda a modelagem e análise de Dispositivos Fotônicos e de RF via códigos home-made e comerciais baseados no método dos elementos finitos (MEF) e, em alguns casos, resolução de problemas inversos com auxílio de AG. Primeiramente é feita uma breve revisão sobre elementos finitos e AG, bem como alguns fenômenos eletromagnéticos voltados às aplicações estudadas. Os estudos de problemas fotônicos abordaram dois problemas gerais: Otimização da banda fotônica proibida absoluta em cristais fotônicos bidimensionais e propostas de fibras de cristais fotônicos (PCFs, Photonic Crystal Fibers) voltadas para aplicações não-lineares e compensação de dispersão. Algumas dessas análises envolveram a resolução de problemas inversos via AG; em que foi proposta uma codificação com certa generalização para problemas envolvendo PCF. As propostas envolvendo RF abordaram antenas para etiquetas RFID (Radio Frequency Identification). Foi explorado o comportamento dual-band a partir de uma antena do tipo dipolo modificada. / Abstract: This dissertation addresses the modeling and analysis of photonic and RF devices by home-made and commercial codes based on the finite element method (FEM). In some cases, inverse problems have been solved with the aid of genetic algorithms (GA). In the introduction a brief review of finite elements and GA are presented as well as some electromagnetic phenomena related with the applications here analyzed. Concerning the photonic problems, our studies were restricted to two general problems: Optimization of absolute photonic band gap in two-dimensional photonic crystals and the proposal of photonic crystal fibers (PCFs) aimed for non-linear and dispersion compensation applications. Some of the analysis involved the solution of inverse problems by means of GA, where, a codification with some generalization to problems involving PCFs was proposed. The proposals involving RF antennas for RFID (radio frequency identification) tags included the study of modified dipole antennas with dual-band operation. / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica
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Dispositivos baseados no preenchimento de fibras de cristal fotônico por líquidos e materiais nanoestruturados / Devices based on the filling of photonic crystal fibers by liquids and nanostructured materialsAlexandre Bozolan dos Santos 17 April 2012 (has links)
Esta tese descreve a demonstração experimental de dispositivos baseados em fibras de cristal fotônico (PCFs), que aproveitam a flexibilidade estrutural oferecida pela matriz de capilares que compõe a seção reta da fibra, de forma a preencher estes capilares com líquidos e materiais nanoestruturados. Para o caso de materiais nanoestruturados, uma vez preenchida a fibra, os materiais nela inseridos interagem eficientemente com a luz guiada. Essa arquitetura diferenciada em relação às fibras ópticas convencionais abre novas perspectivas no desenvolvimento de aplicações como óptica não-linear e sensoriamento. PCFs de núcleo líquido, por outro lado, impõe dificuldades para a implementação de dispositivos práticos, devido às altas taxas de evaporação dos líquidos inseridos. Por esta razão, foi desenvolvida uma nova técnica para vedar seletivamente ambas as faces externas do núcleo líquido de uma PCF, utilizando um polímero curável. Estes tampões poliméricos evitam a evaporação, causando um impacto mínimo no guiamento da luz, tornando o dispositivo usável por semanas. Esta nova técnica de vedação foi empregada em um experimento para a geração de supercontínuo em uma PCF com núcleo de água destilada, proporcionando uma estabilidade de pelo menos 1 hora. Combinando líquidos e materiais nanoestruturados, foi também foi desenvolvido um sensor de temperatura baseado no preenchimento do núcleo de uma PCF por uma amostra coloidal de nanopartículas semicondutoras de CdSe/ZnS, dispersas em óleo mineral. O espectro de luminescência destes pontos quânticos coloidais é fortemente dependente da temperatura e os resultados obtidos mostraram que a grande interação entre a luz e o colóide, aliada a geometria da fibra, proporcionando uma sensibilidade ~5,5 vezes maior que a apresentada por uma rede de Bragg escrita em uma fibra óptica padrão, com boa relação sinal-ruído. / This thesis describes the experimental demonstration of devices based on photonic crystal fibers (PCFs). PCFs are optical fibers whose core is surrounded by a regular matrix of holes, which runs longitudinally across its length. This singular configuration allows the insertion of liquids and nanostructured material into the fiber. Nanostructured materials embedded inside the fiber efficiently interact with the guided light, opening up possibilities of novel applications regarding the fields of non-linear optics, as well as optical sensing. On the other hand, liquid-core PCFs suffer from some disadvantages concerning practical device applications, on account of the high evaporation of the inserted liquids. In order to address this issue, we developed a novel technique to selectively seal the external faces of a liquid-core PCF, by using a polymer plug. These polymer plugs avoid evaporation while causing a minimum impact on the light guiding characteristics of the PCF. This novel sealing technique was employed in a supercontinuum generation experiment, by using a PCF whose core was water-filled. A temporal stability of at least one-hour on the resulting spectrum was achieved. Combining the above techniques, we also developed a temperature sensor based on the core-filling of a PCF by a colloidal ensemble of CdSe/ZnS semiconductor nanoparticles dispersed in mineral oil. Those colloidal quantum-dots display a luminescence spectrum which is strongly dependent on temperature and the experimental results indicated that the greater interaction between the guided light and the colloidal sample, provided by the fiber geometry, allowed a sensitivity which is approximately 5.5 times than possible with a conventional Bragg grating, while keeping a satisfactory signal-to-noise ratio.
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Photonic Crystal Fiber as a Robust Raman BiosensorKhetani, Altaf January 2016 (has links)
This thesis focuses on the investigation and development of an integrated optical biosensor based on enhanced Raman techniques that will provide label-free detection of biomolecules. This is achieved by using hollow core photonic crystal fibers (HC-PCF), nanoparticles, or both. HC-PCF is a unique type of optical fiber, with continuous ‘channels’ of air (typically) running the entire length. The channels serve to confine electromagnetic waves in the core of the fiber, and tailor its transmission properties. Using HC-PCF as a biosensor requires development of a robust technique to fill hollow-core photonic crystal fibers. Though several groups have reported selective filling of HC-PCF’s core, the processes are cumbersome and limit the choice of liquid to avoid multimode behavior. In my Master’s thesis, I presented a simple technique to non-selectively fill all the HC-PCF channels with samples. The non-selective filling preserves the photonic bandgap property of the fiber, and yields an extremely strong interaction of light and the sample that produces considerable enhancement of the Raman signal from the analyte. Up to now, non-selective filling was accomplished through capillary action and it delivered a Raman signal enhancement of approximately 30-fold, which is not sensitive enough to detect biomolecules at the clinical level. Moreover, there were issues of reliability and reproducibility, due to evaporation, filling and coupling light into the fiber.
The objective of this PhD research was to overcome these problems by developing a robust optical fiber platform based on Raman spectroscopy that can be used in a clinical setting. I initially focused on heparin, an important blood anti-coagulant that requires precise monitoring and control in patients undergoing cardiac surgery or dialysis. Since the Raman spectra of heparin-serum mixtures exhibits Raman peaks of heparin with poor signal-to-noise ratios, I concentrated on enhancing the heparin Raman signal and filtering out the spectral background of the serum to improve detection sensitivity. Reaching maximum enhancement of the Raman signal required a strong interaction of light and analyte, which can be achieved by using hollow core photonic crystal fiber as I had used in my Master’s research. Using a small piece of HC-PCF I was able to reach an enhancement in the heparin Raman signal of greater than 90-fold. With this degree of enhancement, I was able to successfully detect and monitor heparin in serum at clinical levels, something that had never been accomplished previously.
After developing HC-PCF as a Raman signal enhancer, I focused on making the HC-PCF sensor robust, reliable and reusable. This was achieved by integrating the HC-PCF with a differential pressure system that allowed effective filling, draining and refilling of the samples in an HC-PCF, under identical optical conditions. To demonstrate the device’s detection capabilities, various concentrations of aqueous ethanol and isopropanol, followed by different concentrations of heparin and adenosine in serum, were successfully monitored.
To further improve the sensitivity of the HC-PCF based Raman sensor, I incorporated surface enhanced Raman scattering (SERS), by introducing nanoparticles into the HC-PCF fibers. The research focused on determining the optimal volume and size of silver nanoparticles to achieve maximum enhancement of the Raman signal in the HC-PCF. The HC-PCF enhanced the Raman signal of Rhodamine 6G (R6G) approximately 90-fold. In addition, the optimal size and volume of AgNP enhanced the Raman signal of R6G approximately 40-fold, leading to a total enhancement of approximately 4,000 in HC-PCF. This was then used to demonstrate the application of a SERS based HC-PCF sensing platform in monitoring adenosine (a clinically important molecule), as well as malignant cells such as leukemia.
Finally, I used hollow core crystal fibers to significantly enhance the efficiency of two-photon photochemistry. Although two-photon photochemical reactions are difficult to achieve with a small volume, I accomplished it by using a novel platform of HC-PCF to efficiently execute the two-photon induced photodecarbonylation reaction of cyclopropenone 1, and its conversion to the corresponding acetylene. The simple optical design configuration involved coupling an 800-nm tsunami laser to a short piece of HC-PCF filled with the sample. This allowed me to increase the efficiency of two-photon induced photochemistry by 80-fold, compared to a conventional spectrophotometer cuvette. Thus, this work leads to the use of HC-PCFs to more effectively study two-photon induced photochemistry processes, which was limited due to the difficulty of detecting photochemical events with a small excitation volume.
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Photon-pair generation in hollow-core photonic-crystal fiber / Génération de paires de photons dans les fibres à cristaux photoniques à coeur creuxCordier, Martin 17 May 2019 (has links)
Les sources de paires de photons sont un composant essentiel des technologies émergentes en information quantique. De nombreux travaux ont permis des avancées importantes utilisant des processus non linéaires d'ordre 2 dans les cristaux et les guides d'ondes, et d'ordre 3 dans les fibres. Les limitations viennent dans le premier cas, des pertes et en particulier des pertes de couplage avec les fibres optiques et dans le second cas, du bruit dû à l'effet Raman dont le spectre est très large dans les fibres de silice. Ce projet propose une nouvelle architecture basée sur des fibres à cristal photonique à coeur creux (FCPCC) que l'on peut remplir de liquide ou de gaz non linéaire. Cette configuration permet la génération paramétrique de paires de photons corrélés par mélange à quatre ondes sans l'inconvénient de la diffusion Raman. Cette technologie offre une large gamme de paramètres à explorer en s'appuyant sur les propriétés physiques et linéaires contrôlables des FCPCC et la possibilité de remplissage de ces fibres avec des fluides aux propriétés non-linéaires variées. En effet, par une conception judicieuse de la FCPCC et un choix approprié du liquide ou du gaz, il est possible de (i) contrôler la dispersion et la transmission pour générer des photons corrélés sur une large gamme spectrale avec la condition d'accord de phase la plus favorable, (ii) d'ajuster la taille de coeur de la fibre et/ou sa forme pour augmenter sa non-linéarité ou son efficacité de couplage avec d'autres fibres et (iii) de s'affranchir totalement de l'effet Raman si on utilise par exemple un gaz monoatomique, ou d'obtenir des raies Raman fines, aisément discriminables des raies paramétriques dans le cas d'un liquide. / Photon pair sources are an essential component of the emerging quantum information technology. Despite ingenious proposals being explored in the recent years based on either second order nonlinear processes in crystals and waveguides or on third order processes in fibers, limitations remain, due to losses and specifically coupling losses in the former case and due to Raman generation in silica, giving rise to a broad spectrum noise in the latter. These limitations have been challenging to lift because of the limited alternative nonlinear materials that fulfil the conditions for the generation of bright and high fidelity photon pairs in integrable photonic structures. In the present project, we develop a new and versatile type of photonic architecture for quantum information applications that offers access to a variety of nonlinear optical materials that are micro-structured in optical fiber forms to generate photon pairs, without the drawback of Raman scattering and with a large design parameter-space. Indeed, with a careful design of the HCPCF along with the appropriate choice of fluid, one can (i) control the dispersion and the transmission to generate photons with the most favourable phase-matching condition over a large spectral range, (ii) adjust the fibre core size and/or shape to enhance nonlinearity or the coupling efficiency with other fibres, (iii) totally suppress the Raman effect in monoatomic gases for instance or have only narrow and separated Raman lines that can thus be easily separated from the useful parametric lines in liquids.
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Experimental study of supercontinuum generation in an amplifier based on an Yb3+ doped nonlinear photonic crystal fiberBaselt, Tobias, Taudt, Christopher, Nelsen, Bryan, Lasagni, Andrés Fabián, Hartmann, Peter 29 August 2019 (has links)
The use of supercontinuum light sources in different optical measurement methods, like microscopy or optical coherence tomography, has increased significantly compared to classical wideband light sources. The development of various optical measurement techniques benefits from the high brightness and bandwidth, as well as the spatial coherence of these sources. For some applications, only a portion of the broad spectral range can be used. Therefore, an increase of the spectral power density in limited spectral regions would provide a clear advantage over spectral filtering. This study describes a method to increase the spectral power density of supercontinuum sources by amplifying the excitation wavelength inside a nonlinear photonic crystal fiber (PCF). An ytterbium doped photonic crystal fiber was manufactured by a nanopowder process (drawn by the company fiberware) and used in a fiber amplifier setup as the nonlinear fiber medium. In order to characterize the fiber’s optimum operational characteristics, group-velocity dispersion (GVD) measurements were performed on the fiber during the amplification process. For this purpose, a notch-pass mirror was used to launch the radiation of a stabilized laser diode at 976 nm into the fiber sample for pumping. The performance of the fiber was compared with a conventional PCF. Finally, the system as a whole was characterized in reference to common solid state-laser-based photonic supercontinuum light sources. An improvement of the power density up to 7.2 times was observed between 1100 nm to 1380 nm wavelengths.
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