Ce travail de thèse porte sur l'étude des processus non-linéaires cohérents des semiconducteurs nanostructurés en microcavité. Cette étude montre la faisabilité d'une porte optique ultra-rapide et peu dissipative fonctionnant avec une faible énergie de commande (~µJ/cm²). Des études expérimentales en diffraction et en pompe-sonde dégénérées ont été réalisées sur des microcavités semiconductrices, à température ambiante. Elles ont permis de mettre en évidence une modulation ultra-rapide de la fonction diélectrique du semiconducteur lorsque l'on excite le matériau dans sa région de transparence. Un rendement de diffraction de 2% et une modulation de réflectivité d'un contraste 5:1 ont été mesuré pour une excitation de faible énergie (~µJ/cm²). Cette modulation ultra-rapide a été attribuée à l'effet Stark optique. L'insertion du matériau non-linéaire dans une microcavité Fabry-Pérot permet d'exalter l'interaction lumière/matière et ainsi d'abaisser l'intensité de commande. Une étude numérique d'une microcavité contenant un milieu absorbant a été réalisée. Nous avons montré que le minimum de réflectivité ne se produit pas forcément à la longueur d'onde de résonance lres attendue mais en une longueur d'onde dite de pseudo-résonance lps. Le décalage entre ces deux longueurs d'onde peut atteindre plusieurs nanomètres. En considérant cette étude, une modélisation du couplage de l'effet Stark optique avec le mode de la cavité a également été réalisée. Le modèle développé permet de rendre compte des résultats expérimentaux de modulation de réflectivité. L'utilisation de ce modèle permettrait d'étudier l'influence des paramètres d'élaboration de la cavité sur la modulation et ainsi de définir une structure adaptée à la modulation.

Orientador: Luís Eduardo Evangelista de Araujo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-18T17:59:31Z (GMT). No. of bitstreams: 1 Carvalho_SilvaniaAlvesde_D.pdf: 4970692 bytes, checksum: f260af26ecacc7e92b1246968850ff9b (MD5) Previous issue date: 2011 / Resumo: Nesta tese apresentamos o estudo teórico de grades de difração induzidas em meios atômicos na condição de transparência induzida eletromagneticamente (EIT). As grades atômicas que serão descritas baseiam-se na não-linearidade Kerr gigante exibida pelos átomos sob EIT. No primeiro estudo realizado, a grade atômica é gerada a partir da modulação da não-linearidade Kerr através de uma onda estacionária. Neste estudo, aplicamos a teoria de ondas acopladas, desenvolvida originalmente para grades acústicas e holográficas, para a grade atômica de modo a obter uma expressão analítica para a eficiência de difração em primeira ordem. Altas eficiências de difração de um feixe de prova ressonante são previstas para incidência próxima ao ângulo de Bragg. Em um segundo estudo, descrevemos uma grade atômica do tipo ¿blazed¿ criada através da inserção de uma máscara de intensidade em um dos feixes responsáveis pela não-linearidade Kerr do meio. Eficiências de difração em primeira ordem para o feixe de prova próximas a 100% foram obtidas. Por último, discutimos uma grade de difração induzida na condição de coerência máxima entre os estados fundamentais de um átomo. Esta grade difrata não somente o feixe de prova incidente, mas também um segundo feixe gerado por mistura de quatro ondas. Apesar desta última grade apresentar eficiência de difração muito menor do que as duas grades anteriores, esta grade pode operar em vários comprimentos de onda diferentes, embora envolva sempre um feixe ressonante com alguma transição atômica. Além da contribuição teórica, trabalhos experimentais relacionados à área de aprisionamento e resfriamento de átomos foram realizados. Inicialmente, um experimento de espectrocopia de fotoassociação próximo ao limite de dissociação em uma amostra de 85Rb é apresentado. Em seguida, uma fonte de laser em 423 nm, formada por um laser de Ti-Sa com dobramento intracavidade através de um cristal LBO, que foi construída e estabilizada é descrita / Abstract: In this thesis we present a theoretical study on induced diffraction gratings in atomic media under electromagnetically induced transparency condition. The atomic gratings which will be described are based on the giant Kerr nonlinearity displayed by the atoms under EIT. In the first study, the atomic grating is generated from the modulation of the Kerr nonlinearity through a stationary wave. In this study, we apply coupled wave theory, originally developed for acoustic and holographic gratings, for an atomic grating in such a way that an analytical expression for the first order diffraction is obtained. High diffraction efficiencies of the resonant probe beam are predicted for incidence near Bragg angle. In a second study, we describe a blazed-type atomic grating created through the insertion of an intensity mask in one of the beam responsible for the Kerr nonlinearity of the medium. First order diffraction for the probe beam near 100% efficiency was observed. Finally, we discuss a diffraction grating induced under maximum coherence condition between the ground states of an atom. This grating diffracts not only the probe beam, but also a second beam generated by four wave mixing. Although this last grating shows a diffraction efficiency much smaller than the previous one, this grating can operate in several wavelengths, although involving a beam resonant with an atomic transition. Besides the theoretical contribution, experimental works related to the cooling and trapping of atoms were implemented. Initially, an experiment of photoassociation spectroscopy near the dissociation limit in a sample of cold rubidium atoms is presented. Following, a homebuilt laser source at 423 nm formed by a Ti-Sapphire laser with intracavity frequency doubling through a LBO crystal that was stabilized is described / Doutorado / Física Atômica e Molecular / Doutora em Ciências

Orientador: Jose Antonio Siqueira Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-15T01:30:18Z (GMT). No. of bitstreams: 1 Costa_EduardoFerreirada_M.pdf: 6728170 bytes, checksum: 22e2ac4dad3b06f3f61e0ece70fa2f5d (MD5) Previous issue date: 2009 / Resumo: Por serem eletricamente passivos e imunes à interferência eletromagnética, os sensores a fibra óptica estão se tornando uma excelente escolha para o sensoreamento em várias aplicações, como aeroespacial, distribuição e geração de energia elétrica, transportes ferroviários, e equipamentos de segurança militares. Entre outras vantagens está o fato de que os sinais medidos podem ser transmitidos em distâncias muito grandes (da ordem de quilômetros), são compactos e leves. A técnica de medida convencional com sensor à FBG necessita de equipamentos de custo muito elevado, tornando-se inviável para aplicações de baixo custo. Neste trabalho apresenta-se uma nova técnica para medir temperatura com sensores a fibra óptica com grades de Bragg. Resultados experimentais de medidas feitas com a técnica desenvolvida mostram que é possível obter uma resolução de 0,5 mºC em medidas realizadas numa faixa de 30ºC. / Abstract: Due to the characteristic of being electrically passive and immune to electromagnetic interference, optical fiber sensors are becoming an excellent choice for several applications, as aerospace, distribution and generation of electrical energy, railway transports, and military equipment. Among other advantages, these sensors are compact, light and the measured signals can be transmitted for very long distances (in the order of kilometers). The existing techniques for temperature measurement using FBG sensors need expensive equipments, and therefore are not suitable for low cost applications. In this work a new technique to measure temperature with a extremely high resolution using FBG sensors is presented. Experimental results of measurements carried out with the proposed technique show that a resolution of 0.5 m°C was obtained for measurements performed over a 30 ºC temperature range. / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Orientadores: Hugo Enrique Hernandez Figueroa , Júlio César Rodrigues Fernandes de Oliveira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-26T03:17:30Z (GMT). No. of bitstreams: 1 Freitas_AlexandrePassos_M.pdf: 2935936 bytes, checksum: 2bf660b1a9d7a183bc552d3db9da1b97 (MD5) Previous issue date: 2014 / Resumo: O crescente aumento da demanda de tráfego de dados dos sistemas de comunicação ópticos em conjunto com a busca da integração e miniaturização cada vez maior dos componentes impulsionaram a fotônica integrada em silício como uma das tecnologias promissoras para a evolução das novas gerações de dispositivos ópticos. Esta tecnologia, além de possuir suas características de um alto contraste de índice de refração, capacidade de modulação óptica através de controle de temperatura ou por densidade de portadores, se utiliza da infra-estrutura de fabricação para a indústria de microeletrônica já desenvolvida nas últimas décadas. Neste cenário, este trabalho propõe o desenvolvimento de um modulador de fase fabricado com a tecnologia de fotônica integrada em silício para o formato de modulação DP-QPSK e que opere na banda C de comunicação óptica. Análises de simulações e experimentais foram realizadas para a validação do fluxo de desenvolvimento do circuito e de cada componentes utilizado individualmente / Abstract: The increasing demand for data in optical communication systems with a constant search for reduction of device dimensions boosted silicon photonics as a candidate technology to the following optical device generations. Besides having high refractive index contrast, modulation capabilities through thermal or by carrier density control, this technology takes advantage of the microelectronic infra-structure developed in the last decades to fabricate small optical components with high reliability. In this scenario, this dissertation proposes the design of a phase modulator in silicon photonic technology. This modulator is able to operate at C-band and make the DP-QPSK modulation. Simulation and experiment analysis were made to validate the design flow for the optical circuit and for each single component / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Reliability and sensitive information protection are critical aspects of integrated circuits. A novel technique using near-field evanescent wave coupling from two subwavelength gratings (SWGs), with the input laser source delivered through an optical fiber is presented for tamper evidence of electronic components. The first grating of the pair of coupled subwavelength gratings (CSWGs) was milled directly on the output facet of the silica fiber using focused ion beam (FIB) etching. The second grating was patterned using e-beam lithography and etched into a glass substrate using reactive ion etching (RIE). The slightest intrusion attempt would separate the CSWGs and eliminate near-field coupling between the gratings. Tampering, therefore, would become evident. Computer simulations guided the design for optimal operation of the security solution. The physical dimensions of the SWGs, i.e. period and thickness, were optimized, for a 650 nm illuminating wavelength. The optimal dimensions resulted in a 560 nm grating period for the first grating etched in the silica optical fiber and 420 nm for the second grating etched in borosilicate glass. The incident light beam had a half-width at half-maximum (HWHM) of at least 7 µm to allow discernible higher transmission orders, and a HWHM of 28 µm for minimum noise. The minimum number of individual grating lines present on the optical fiber facet was identified as 15 lines. Grating rotation due to the cylindrical geometry of the fiber resulted in a rotation of the far-field pattern, corresponding to the rotation angle of moiré fringes. With the goal of later adding authentication to tamper evidence, the concept of CSWGs signature was also modeled by introducing random and planned variations in the glass grating. The fiber was placed on a stage supported by a nanomanipulator, which permitted three-dimensional displacement while maintaining the fiber tip normal to the surface of the glass substrate. A 650 nm diode laser was fixed to a translation mount that transmitted the light source through the optical fiber, and the output intensity was measured using a silicon photodiode. The evanescent wave coupling output results for the CSWGs were measured and compared to the simulation results.

[EN] The present PhD thesis deals on the model, design and experimental demonstration of Arrayed Waveguide Grating (AWG) with advanced features. Firstly, building upon existing AWG formulations, design equations are provided, libraries developed and all this is experimentally validated with devices in Indium Phosphide (InP) and Silicon-on-insulator (SOI) technologies. Next, a model and experimental validation is reported for an Interleave-Chirped Arrayed Waveguide Grating (IC-AWG), which is able to process optical signals as WDM demultiplexer, polarization splitter and phase diversity component all in a single device. This device was fabricated and tested in InP technology. The second innovative AWG demonstrated in this thesis, a Reflective type (R-AWG), whose layout allows for tailoring the pass-band shape and to change the spectral resolution. A demonstration of design and fabrication for this device is provided in SOI technology. The last AWG with innovative concepts is one driven by Surface Acoustic Waves (AWG-SAW), where the spectral channels can be tuned by means of acousto-optic effect. The device was fabricated in Aluminium Gallium Arsenide (AlGaAs) technology, and measurements are provided to validate the concept and design flow. In parallel this thesis has resulted in the development of different AWG layouts for a wide number of (generic) technologies and foundries, coded into design libraries, of use in a de-facto standard software employed for the design of photonic integrated circuits. These design libraries have been licensed to the UPV spin-off company VLC Photonics S.L. / [ES] La presente tesis se ha centrado en el modelado, diseño y demostración experimental del dispositivo Arrayed Waveguide Grating (AWG) con funcionalidades avanzadas. Primero, usando la formulación existente sobre AWGs se aportan ecuaciones y librerías de diseño, y se validan experimentalmente por medio de dispositivos fabricados en tecnologías de Indium Phosphide (InP) y Silicon-on-insulator (SOI). Después, se reporta un modelo y demostración experimental para un Interleave-Chirped Arrayed Waveguide Grating (IC-AWG), el cual es capaz de procesar señales ópticas como demultiplexor WDM, divisor de polarización y componente de diversidad de fase en un único dispositivo. Este dispositivo fue fabricado y probado en tecnología de InP. El segundo AWG innovador demostrado en esta tesis es de tipo Reflectante (R-AWG), cuyo diseño permite modificar la forma espectral del canal y cambiar su resolución espectral, incluyendo una demostración de diseño y fabricación de este dispositivo en tecnología de SOI. El último AWG que incluye conceptos innovadores es uno sintonizable por Acoustic Waves (AWGSAW), donde los canales espectrales pueden ser sintonizados por medio del efecto acusto-óptico. Dicho dispositivo fue fabricado en tecnología de Aluminium Gallium Arsenide (AlGaAs), y se han incluido medidas experimentales para validar el concepto y el flujo de diseño. En paralelo junto con esta tesis se han desarrollado diferentes diseños para el AWG en un amplio número de tecnologías (genéricas) y plataformas de fabricación, implementadas en unas librerías de diseño para uno de los softwares m¿as utilizados para el diseño de circuitos integrados ópticos, siendo actualmente el estándar de facto. Dichas librerías de diseño han sido licenciadas a la compañía VLC Photonics S.L., spin-off de la UPV. / [CAT] La present tesi ha estat centrada en el modelatge, disseny i demostració experimental del dispositiu Arrayed Waveguide Grating (AWG) amb funcionalitats avançades. Primer, usant la formulació existent sobre AWGs s'aporten equacions i llibreries de disseny, i es validen experimentalment per mitjà de dispositius fabricats en tecnologies de Indium Phosphide (InP) i Silicon-on-insulator (SOI). Després, es reporta un model i demostració experimental per a un Interleave-Chirped Arrayed Waveguide Grating (IC-AWG), el qual és capaç de processar senyals òptiques com demultiplexor WDM, divisor de polarització i component de diversitat de fase en un únic dispositiu. Aquest dispositiu va ser fabricat i provat en tecnologia de InP. El segon AWG innovador demostrat en aquesta tesi és de tipus Reflector (R-AWG), amb un disseny que permet modificar la forma espectral del canal i canviar la seua resolució espectral, incloent una demostració de disseny i fabricació d'aquest dispositiu en tecnologia de SOI. L'últim AWG que inclou conceptes innovadors és un sintonitzable per Acoustic Waves (AWG-SAW), on els canals espectrals poden ser sintonitzats per mitjà de l'efecte acusto-òptic. Aquest dispositiu va ser fabricat en tecnologia de Aluminium Gallium Arsenide (AlGaAs), i s'han inclòs mesures experimentals per validar el concepte i el flux de disseny. En paral.lel juntament amb aquesta tesi s'han desenvolupat diferents dissenys per al AWG en un ampli nombre de tecnologies (genèriques) i plataformes de fabricació, implementades en unes llibreries de disseny per a un dels programaris més utilitzats per al disseny de circuits integrats òptics, sent actualment l'estàndard de facto. Aquestes llibreries de disseny han estat llicenciades a la companyia VLC Photonics S.L., spin-off de la UPV. / Gargallo Jaquotot, BA. (2016). Advanced arrayed waveguide gratings: models, design strategies and experimental demonstration [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/74646 / TESIS

In my research work, I study diffraction by planar periodic structures (diffraction grating). In the first chapter, I try to familiarize the importance of diffraction gratings in spectroscopy. The second chapter explains the basic principle of diffraction without involving difficult mathematical tools. In the third chapter, I deduce Fourier modal method from Maxwell equations, a modern mathematical approach used for calculating the electromagnetic response of diffraction. The most important part of my work consists of the fourth and fifth chapter. At first, I try to utilize Fourier modal method for deriving formulas involving just 0th and (-1)st diffraction orders. Because of the unreasonable difficulty of uncovered formulas, I decided to consider only a special case - so-called Littrow configuration, in which the solution can be superposed from symmetric and antisymmetric couples of rays. I further develop so-called Local modal method - very inaccurate, but mathematically fairly simple, and discuss its physical limitations. Whole work is finished by the sixth chapter, which compares accurate computations gained from simulation and derived analytical formulas for both methods.

Title: Surface plasmons in optical microstructures and their sensor applications Author: Pavel Adam Institute: Institute of Photonics and Electronics AS CR, v.v.i., Department of Optical Sensors Supervisor of the doctoral thesis: doc. Ing. Jiří Homola, CSc., DSc. Abstract: This work is focused on the study of surface plasmon resonance (SPR) sensor platforms based on wavelength division multiplexing (WDM) of multiple surface plasmons (SPs). These sensors are based on advanced diffraction gratings supporting either conventional or Bragg-scattered SPs, which are simultaneously excited at different wavelengths. These SPs are studied both analytically and numerically using rigorous coupled-wave analysis and an integral approach. WDM of two and three SPs is presented and followed by the method for the analysis of the resolution, noise and cross-sensitivity. This method is employed to analyze the ability of different SPR sensor platforms (supporting WDM of two SPs) to discriminate refractive index (RI) changes in a thin layer at the sensor surface from background RI changes. The WDM SPR sensors based on advanced diffraction gratings prepared by interferometric holography are developed and tested in a model biosensing experiment consisting of the layer-by-layer growth of protein multilayers. The linear WDM of two...

Bragg scattering of optical waves in thick gratings at extreme angles, where the scattered wave propagates parallel (extremely asymmetric scattering - EAS) or nearly parallel (grazing angle scattering - GAS) to the grating boundaries, is associated with many unique and practically important resonant phenomena. It has been demonstrated that one of the main physical mechanisms for these resonant phenomena is the diffractional divergence of the scattered wave inside and outside the grating region. This thesis fills the gaps in the theoretical and experimental understanding of Bragg scattering in gratings at extreme angles by investigating EAS and GAS in structures where diffractional divergence of waves is significantly affected by anisotropy and/or non-uniformities of the dielectric permittivity. Unusually high sensitivity of wave scattering in thick periodic gratings to small step-like variations of mean structural parameters at the grating boundaries is predicted and described for the case when the scattered wave (the +1 diffracted order) propagates almost parallel to the front grating boundary (the geometry of GAS). A unusual pattern of strong multiple resonances for bulk electromagnetic waves is predicted and analysed numerically in thick periodic holographic gratings in a guiding slab with mean permittivity that is greater than that of the surrounding media. It is demonstrated that these resonances are related to resonant generation of a new type of eigenmodes in a thick slab with a periodic grating. These eigenmodes are generically related to the grating -- they do exist not if the grating amplitude is zero. A new type of resonant coupling of bulk radiation into the conventional guided modes of a slab with a thick holographic grating is predicted and explained theoretically. It occurs in the presence of strong frequency detunings of the Bragg condition by means of interaction of the strongly non-eigen +1 diffracted order with the slab-grating boundaries. Therefore, it is only in the presence of step-like variations of the mean permittivity at the grating boundaries that this type of resonant coupling can occur. A new method for the analysis of EAS and GAS in anisotropic gratings is developed. This method is based on the consideration of the diffractional divergence of the scattered wave and the two-wave approximation in anisotropic gratings. Special efforts are focused on the analysis of EAS and GAS of extraordinary waves in uniaxial gratings. In particular, it is demonstrated that increasing curvature of the normal surface in the direction of propagation of the scattered wave results in increase of its diffraction divergence and the resonant amplitude. A theoretical model is developed for comparison of the theoretical predictions with data obtained from experimental observations of EAS in a holographic grating written in a photorefractive medium. The developed model is applied for the interpretation of experimental observations of EAS in BaTiO3 photorefractive crystals. Good agreement with the theoretical predictions is demonstrated.

Dans les systèmes optiques modernes, l'importance des composants holographiques ne cesse d'augmenter. Parmi les matériaux holographiques disponibles, la gélatine bichromatée se distingue par la très bonne qualité des hologrammes obtenus. Cette thèse décrit la mise au point de techniques de fabrication et de caractérisation de composants holographiques en gélatine bichromatée. L'interprétation des mesures de caractérisation s'appuie sur une modélisation approfondie de la diffraction par des structures périodiques: une nouvelle méthode de résolution de la théorie d'ondes couplées, plus stable numériquement que les précédentes, est proposée. De plus, la théorie de la diffraction par des réseaux est étendue a des cas importants de restitution en lumière quasi-monochromatique. Les dispositifs expérimentaux développés ont permis l'étude et la réalisation de quatre nouveaux types d'hologrammes: réseaux pour la compression temporelle d'impulsions ultra brèves, hologramme synthétique séparateur et uniformiseur de faisceau laser, lentille holographique pour diode laser infrarouge et hologramme en ligne pour la réplication globale de disques compacts.