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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Desenvolvimento de pentes de frequências ópticas para metrologia e espectroscopia de precisão / Development of optical frequency combs for precision metrology and spectroscopy

Nogueira, Giovana Trevisan 15 February 2007 (has links)
Orientador: Flavio Caldas da Cruz / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-09T02:45:38Z (GMT). No. of bitstreams: 1 Nogueira_GiovanaTrevisan_D.pdf: 19393516 bytes, checksum: a3b51900ea17f278fbdc63e608d828d4 (MD5) Previous issue date: 2007 / Resumo: No final da década de 90, pentes de freqüências ópticas baseados em lasers de Ti:safira de modos travados tornaram-se uma importante ferramenta na área de metrologia. Eles têm sido usados, por exemplo, em medidas diretas de freqüências de várias centenas de THz e em relógios atômicos ópticos. Para a implementação de dois sistemas de pentes de freqüências ópticas, desenvolvemos neste trabalho dois lasers de Ti:safira de femtossegundos de alta taxa de repetição, que usam espelhos de varredura (chirped mirros) no lugar de prismas para compensar a dispersão em velocidade de grupo. Um dos lasers tem taxa de repetição em 770 MHz que pode ser facilmente ajustada entre 750 MHz and 1 GHz. A dispersão total da cavidade é de -60 fs2 , produzindo um espectro centrado em 780 nm com largura a meia altura em torno de 10 nm e pulsos de 150 fs. Este laser teve seu espectro alargado por duas fibra de microestrutura, cobrindo um intervalo de 510 à 1100 nm. O outro laser possui cavidade com taxa de repetição sintonizável entre 1 e 2,12 GHz, e um espectro que se estender de de 585 até 1200 nm a -20 dB abaixo do máximo em 986 nm sem o uso de fibra de microestrutura.A cavidade do laser tem dispersão total próxima de zero, porém com oscilações entre -50 a +100 fs2 entre 700 nm e 900 nm, que foi medida por interferometria de luz branca. Nós mostramos que cerca de 17 % (76 %) da potência intracavidade (de saída) é gerada basicamente por efeitos não lineares em passagem única no cristal de Ti:safira, observada na região verde do espectro e entre 960 nm e 1200 nm, fora da banda da cavidade laser e onde o ganho do cristal de Ti:safira é baixo. Ambos os lasers tiveram suas taxas de repetição medidas e estabilizadas em relação a osciladores estáveis, podendo ser sintonizados em um intervalo de 30 kHz através do oscilador de referência. Construímos interferômetros de Michelson e Mach-Zender para a medida do deslocamento entre onda portadora e envelope do pulso do sistema do laser cujo espectro é ampliado pela fibra. O batimento entre freqüências do pente próximas a 520 nm e o segundo harmônico da parte do espectro em 1040 nm é medido em um fotodetector rápido. Estes sistemas serão inicialmente utilizado em um relógio atômico óptico baseado na transição de intercombinação de átomos de cálcio frios e aprisionados. Entretando, além de aplicações em metrologia de tempo e freqüência, os pentes de freqüências ópticas podem ser ferramentas atrativas para uso em espectroscopia atômica e molecular de precisão e estudos de dinâmicas rápidas que exploram a combinação de alta resolução e cobertura espectral larga fornecidas pelo pente de freqüências / Abstract: Optical frequency combs based on femtosecond Ti:sapphire lasers and introduced at the end of the 90s have revolutionized the optical metrology field. They have allowed ultraprecise optical spectroscopy, by direct measurement of frequencies of several hundred THz, and the development of optical atomic clocks . To implement optical frequency combs, we have to stabilize both the repetition rate and the carrier-to-envelope oÿset frequency of the femtosecond laser. We have developed two versions of optical frequency combs based on high-repetition rate femtosecond Ti:sapphire lasers, which use chirped mirrors instead of prisms for compensating the group velocity dispersion. The combs will be initially used in an optical atomic clock based on the intercombination transition of cold and trapped calcium atoms. One of our fsec Ti:sapphire lasers has a repetition rate that can be easily adjusted between 750 MHz and 1 GHz. The total dispersion of the cavity is -60 fs2 . It produces pulses of 150 fs with a spectrum centered at 780 nm, with a width of 10 nm. The spectrum of this laser has been broadened with a microstructure fiber, and covers an optical octave extending from 520 and 1040 nm. The other fsec Ti:sapphire laser has a repetition rate that can be changed from 1 to 2.12 GHz, and a spectrum that extends from 585 nm to 1200 nm, without use of microstructure fibers. These wavelengths are points in the spectrum at -20 dB below the maximum at 986 nm. The laser cavity has total intracavity dispersion near zero, but with oscillations from -50 to +100 fs2 between 700 to 900 nm, that have been measured by white light interferometry. We showed that 17 % (76 %) of the intracavity (output) power is generated by nonlinear effects in a single pass through the crystal, and with a spectral distribution concentrated between 960 nm and 1200 nm, thus outside the laser cavity bandwidth and where the Ti:sapphire gain is lower. Emission in the green has also been observed, which is also outside the laser cavity bandwidth and the emission gain profile of the Ti:sapphire crystal. The repetition rate of both lasers have been phase-locked to stable microwave oscillators, and could also be frequency tuned in a range of 30 kHz with respect to the reference oscillator. We have built f-2f interferometers to measure the carrier-to-envelope oÿset frequency of the laser whose spectrum is broadened by the microstructure fiber. Comb frequencies near 540 nm are heterodyned in a fast photodetector with the second harmonic of the comb light at 1080 nm. In addition to applications in optical time and frequency metrology, the optical frequency combs should be attractive tools for use in precision atomic and molecular spectroscopy, coherent control which exploits the coherent accumulation effect, and studies of fast time dynamics that take advantage of the combination of the ultra high resolution and broadband spectral coverage provided by the comb / Doutorado / Ótica / Doutor em Ciências
32

Fabrication and Characterization of Silicon Photonic Devices

Abdullah Al Noman (11251179) 11 August 2021 (has links)
Silicon photonics has become one of the leading candidates for the next generation optical communication platform. In addition to being an inexpensive material and compatible with Complementary metal–oxide–semiconductor (CMOS) manufacturing, silicon exhibits low absorption at optical telecommunication bands. However, high propagation loss and poor light confinement in narrow Si waveguides have limited high-density optical integration.<br>In this work, we show the fabrication and characterization of a novel type of devices named E-skid devices that can reduce the skin depth and suppress the large spatial content of evanescent light. These devices use artificial anisotropic dielectric metamaterial to suppress the evanescent waves. Beside E-skid devices, we also discuss the fabrication and experimental characterization of mode filters using Silicon on Insulator that can block the fundamental TE0 and allow the higher order modes to pass through using Multi Mode Interference.<br>In this work, the mode is filtered using radiation, not by reflection.<br>Beside Silicon, Silicon Nitride has also gained much interest because of its low loss, smaller nonlinear absorption and higher Kerr effect. Silicon Nitride waveguides have widely<br>been used for lots of applications specially the optical frequency comb generation. One special case of coherent optical frequency comb is Soliton in which case the non-linearity and dispersion cancel each other’s effect and keep the pulse without distortion. In this work, we described the Silicon Nitride fabrication process and did a comparative analysis with other research groups who fabricates similar devices. We tried to improve our process by inserting a few additional steps in our fabrication process. We also investigated our process step by step and found out reasons for our low quality factor and low yield. We found a few factors that might be responsible for the low quality factor and addressed them. We fabricated real devices using our modified process and saw improvement in quality factors, yield and thermal performance of the devices.<br>Finally, we describe an edge polishing method for Silicon Nitride microring resonator devices, which we developed from scratch and we can polish edges down to sub-micron level. Thus, the edges become optically flat and it allowed us to do heterogeneous integration with an Indium Phosphide chip. This paves away for some exciting opportunities like on-chip frequency comb generation.<br><br>
33

Časoprostorová dynamika a koherentní řízení frekvenčních hřebenů kvantových kaskádových laserů / Spatio-temporal dynamics and coherent control of quantum cascade laser frequency combs

Konečný, Aleš January 2021 (has links)
Kvantové kaskádové laserové frekvenční hřebeny jsou slibnými kandidáty pro nové miniaturizované spektrometry bez pohyblivých částí. Mohou být generovány v samočinném režimu pomocí různých nelinearit vyvolaných asymetrickým ziskem a vlnovodovou disperzí. K simulaci samočinných hřebenů byl použit dostupný vysoce optimalizovaný nástroj založený na modelu postupné vlny. Dále byl rozšířen o funkci zamykání optickým vstřikováním, koherentní techniky ovládání frekvenčních hřebenů. Následné simulace potvrdily uzamčení pomocí vstřikovaného signálu. Bylo zjištěno, že disperze grupové rychlosti (GVD) má významný dopad na rozsah zamykání. GVD byla vypočtena pro typické zařízení a frekvenční hřeben byl uzamčen pomocí optického vstřikování v rozsahu ladění od -2 do 47 MHz.
34

Optical frequency comb generation using InP based quantum-dash/ quantum-well single section mode-locked lasers / Génération de peignes de fréquences optiques à l’aide de lasers à verrouillage de modes mono-section, à base de bâtonnets et puits quantiques élaborés sur InP

Panapakkam Venkatesan, Vivek 05 December 2016 (has links)
Les interconnections optiques dans les fermes de données (data centers) nécessitent la mise au point de nouvelles approches technologiques pour répondre aux besoins grandissants en composants d’interface respectant des cahiers de charge drastiques en termes de débit, coût, encombrement et dissipation d’énergie. Les peignes de fréquences optiques sont particulièrement adaptés comme nouvelles sources optiques, à mêmes de générer un grand nombre de porteuses optiques cohérentes. Leur utilisation dans des systèmes de transmission en multiplexage de longueurs d’onde (WDM) et exploitant de nouveaux formats de modulation, peut aboutir à des capacités jamais atteintes auparavant. Ce travail de thèse s’inscrit dans le cadre du projet européen BIG PIPES (Broadband Integrated and Green Photonic Interconnects for High-Performance Computing and Enterprise Systems) et a pour but l’étude de peignes de fréquences générés à l’aide de lasers à verrouillage de modes, à section unique, à base de bâtonnets quantiques InAs/InP et puits quantiques InGaAsP/InP. Nous avons entrepris l’étude de nouvelles couches actives et conceptions de cavités lasers en vue de répondre au cahier des charges du projet européen. Une étude systématique du bruit d’amplitude et de phase de ces sources a en particulier été menée à l’aide de nouvelles techniques de mesure afin d’évaluer leur compatibilité dans des systèmes de transmission à très haut débit. Ces peignes de fréquences optiques ont été utilisées avec succès dans des expériences de transmission sur fibre optique avec des débits records dépassant le Tbit/s par puce et une dissipation raisonnable d’énergie par bit, montrant leur fort potentiel pour les applications d’interconnections optiques dans les fermes de données / The increasing demand for high capacity, low cost, high compact and energy efficient optical transceivers for data center interconnects requires new technological solutions. In terms of transmitters, optical frequency combs generating a large number of phase coherent optical carriers are attractive solutions for next generation datacenter interconnects, and along with wavelength division multiplexing and advanced modulation formats can demonstrate unprecedented transmission capacities. In the framework of European project BIG PIPES (Broadband Integrated and Green Photonic Interconnects for High-Performance Computing and Enterprise Systems), this thesis investigates the generation of optical frequency combs using single-section mode-locked lasers based on InAs/InP Quantum-Dash and InGaAsP/InP Quantum-Well semiconductor nanostructures. These novel light sources, based on new active layer structures and cavity designs are extensively analyzed to meet the requirements of the project. Comprehensive investigation of amplitude and phase noise of these optical frequency comb sources is performed with advanced measurement techniques, to evaluate the feasibility of their use in high data rate transmission systems. Record Multi-Terabit per second per chip capacities and reasonably low energy per bit consumption are readily demonstrated, making them well suited for next generation datacenter interconnects
35

Frequency Comb Experiments and Radio Frequency Instrumentation Analysis for Optical Atomic Clocks

Ryan J Schneider (14187461) 29 November 2022 (has links)
<p>Space-based global navigation and precision timing systems are critical for modern infrastructure. Atomic clock technology has increased the precision of these systems so that they are viable for military operations, navigation, telecommunications, and finance. Advances in optical atomic clocks, based on optical frequencies, provide an opportunity for even more precise timing. Therefore, developments in chip-scale optical atomic clock technologies could lead to increased and more wide-spread application of this precision timing. One component of the optical atomic clock is the optical frequency comb which serves as an interface between optical and microwave frequencies. This thesis will cover experiments related to these optical frequency combs. A 2$\mu$m fiber laser was developed in order to test second harmonic devices required to stabilize an optical frequency comb. The laser was then employed to measure the operating wavelengths and efficiencies of non-linear devices. In addition, an analysis of the radio frequency instruments used to evaluate microwave outputs was conducted to determine whether a digital signal analyzer (oscilloscope) or an analog electronic spectrum analyzer provides more accurate results for optical frequency comb based experiments.</p>
36

Spectroscopie Laser avec des cavités résonantes de haute finesse couplées à un peigne de fréquences : ML-CEAS et vernier effet techniques. Applications à la mesure in situ de molécules réactives dans les domaines UV et visible. / Cavity enhanced multiplexed comb spectroscopy : ML-CEAS and Vernier effect techniques Application : a UV Spectrometer for in situ measurements of reactive molecules.

Abd Alrahman, Chadi 25 October 2012 (has links)
La communauté de la chimie atmosphérique souffre d'un manque de mesures rapides, fiables résolues spatialement et temporellement pour un large éventail de molécules réactives (radicaux tels que NO2, OH, BrO, IO, etc). En raison de leur forte réactivité, ces molécules contrôlent largement la durée de vie et la concentration de nombreuses espèces clés dans l'atmosphère, et peuvent avoir un impact important sur le climat. Les concentrations de ces radicaux sont extrêmement faibles (ppbv ou moins) et très variable dans le temps et dans l'espace, ce qui impose un véritable défi lors de la détection. Dans la première partie de cette thèse, un spectromètre UV robuste, compacte et transportable est développé, exploitant la technique ML-CEAS pour mesurer à des niveaux très faibles (pptv et même en dessous) des molécules réactives d'importance atmosphérique, en particulier, les radicaux d'oxyde d'halogènes, afin de répondre aux besoins émergents. La technique ML-CEAS est basée sur le couplage d'un laser femtoseconde à blocage de modes à une cavité optique de haute finesse, qui agit comme un piège à photons pour augmenter l'interaction entre la lumière et l'échantillon de gaz intracavité. Cela permet d'améliorer fortement la sensibilité d'absorption. La limite de détection obtenue pour le radical IO est de 20 ppqv pour un temps d'acquisition de 5 minutes, ce qui est un résultat impressionnant. Dans la deuxième partie de cette thèse, une nouvelle technique spectroscopique est développée appelée effet Vernier, qui est également basé sur l'interaction entre un laser femtoseconde à blocage de mode et une cavité optique de haute finesse. Cette technique fournit une sensibilité de détection similaire à la technique ML-CEAS, mais l'avantage est que le nombre des éléments spectraux est donné par la finesse de la cavité optique et donc peut atteindre plusieurs dizaines de milliers. De plus, cette configuration simplifie le montage expérimental par la suppression du spectrographe qui est remplacé par une simple photodiode. Le temps d'acquisition d'un spectre peut être aussi réduit à moins d' 1 ms. / The atmospheric chemistry community suffers a lack of fast, reliable and space resolved measurements for a wide set of reactive molecules (e.g. radicals such as OH, NO3, BrO, IO, etc). Due to their high reactivity, these molecules largely control the lifetime and concentration of numerous key atmospheric species, and may have an important impact on the climate. The concentrations of such radicals are extremely low (ppbv or less) and highly variable in time and space, which imposes a real challenge during the detection. In the first part of this thesis, a compact, robust and transportable UV spectrometer is developed, exploiting the Mode-Locked Cavity Enhanced Absorption Spectroscopy (ML-CEAS) technique to measure pptv and sub-pptv levels of atmospherically important reactive molecules, in particular, halogen oxide radicals, to respond to the emerging needs. The ML-CEAS technique is based on coupling a Mode-Locked femtosecond laser to a high finesse optical cavity, which acts as a photon trap to increase the interaction between the light and the intracavity gas sample, which highly enhances the absorption sensitivity. The detection limit obtained for the IO radical is 20 ppqv (part per quadrillion), which is an impressive result. In the second part of this thesis, a new spectroscopic technique is developed, called Vernier effect, which is also based on the interaction between a mode-locked femtosecond laser with a high finesse optical cavity. This technique provides detection sensitivity similar to that of ML-CEAS technique, but the advantage is that the number of the spectral elements is given by the cavity finesse, so it can reach ten thousands, as well as this technique has a simple setup, where the spectrograph is replaced by a photodiode. Additionally, the time required to measure one output absorption spectrum can be less than 1 ms.
37

LIGHT-MATTER INTERACTION FROM ATOMISTIC RARE-EARTH CENTERS IN SOLIDS TO MASSIVE LEVITATED OBJECTS

Xiaodong Jiang (10524008) 19 April 2022 (has links)
<p>  </p> <p>A harmonic oscillator is a ubiquitous tool in various disciplines of engineering and physics for sensing and energy transduction. The degrees of freedom, low noise oscillation, and efficient input-output coupling are important metrics when designing sensors and transducers using such oscillators. The ultimate examples of such oscillators are quantum mechanical oscillators coherently transducing information or energy. Atoms are oscillators whose degrees of freedom can be controlled and probed coherently by means of light. Elegant techniques developed during the last few decades have enabled us to use atoms, for example, to build exquisite quantum sensors such as clocks with the precision of <1 second error over the lifetime of the universe, to store and transduce information of various forms and also to develop quantum processors. Similar to atoms, mechanical oscillators can also be controlled ultimately to their single vibrational quanta and be used for similar sensing and transduction applications.</p> <p><br></p> <p>In this thesis, we explore both atomic and mechanical systems and develop a toolbox to build an effective atom-light interface and light-oscillator interface for controlling such atomic and mechanical oscillators and use them in sensing and storage applications. Primarily, we study two disparate platforms: 1) rare-earth ions in solids integrated into photonic chips as a compact and heterogeneous platform and 2) nanoscopic and macroscopic oscillators interfaced with light and magnetic field to isolate them from environmental noise. </p> <p><br></p> <p>Rare earth (RE) ions in crystals have been identified as robust optical centers and promising candidates for quantum communication and transduction applications. Lithium niobate (LN), a novel crystalline host of RE ions, is considered as a viable material for photonic system integration because of its electro-optic and integration capability. This thesis first experimentally reports the activation and characterization of LN crystals implanted with Yb and Er ions and describes their scalable integration with a silicon photonic chip with waveguide and resonator structures. The evanescent coupling of light emitted from Er ions with optical modes of waveguide and microcavity and modified photoluminescence (PL) of Er ions from the integrated on-chip Er:LN-Si-SiN photonic device with quality factor of 104 have been observed at room temperature. This integrated platform can ultimately enable developing quantum memory and provide a path to integrate more photonic components on a single chip for applications in quantum communication and transduction.</p> <p><br></p> <p>Optomechanical systems are also considered as candidates for light storage and sensing. In this thesis, we also present results of the theoretical study of coherent light storage in an array of nanomechanical resonators. The majority of the thesis is focusing on an optomechanical sensing experiment based on levitation. An oscillator well isolated from environmental noise can be used to sense force, inertia, torque, and magnetic field with high sensitivity as the interaction with these quantities can change the amplitude or frequency of the oscillator’s vibration, which can be accurately measured by light. It has been proposed that such levitated macroscopic objects could be used as quantum sensors and transducers at their quantum ground states. They are also proposed as a platform to test fundamental physics such as detecting gravitational waves, observing macroscopic quantum entanglement, verifying the spontaneous collapse models, and searching for dark matter.</p> <p><br></p> <p>In particular, we consider superconducting levitation of macroscopic objects in vacuum whose positions are measured by light. We build an optomechanical platform based on a levitated small high reflective (HR)-coated mirror above a superconductor disk. We use this levitated mirror at ambient conditions to detect the magnetic field with a sensitivity on the order of <em>pT/sqrt(Hz).</em> Moreover, the levitated mirror is used as the end mirror of a Fabry–Pérot cavity to create an optical resonance that could be used to study coherent radiation pressure forces. The platform provides a sensitive tool to measure the various forces exerted on the mirror and it offers the possibility of the coherent optical trapping of macroscopic objects and precision gravity sensing. Moreover, we study the nonlinear dissipation and mode coupling of a levitated HR-coated magnetic mirror above a superconducting disk in vacuum conditions. We observe that by exciting one vibrational mode of the mirror, the vibrational noise of another mode can be significantly suppressed by a factor of 60. We attribute this unique noise suppression mechanism to the mode coupling and nonlinear dissipation caused by the driven magnetic inhomogeneity of the levitated object. Such a suppression mechanism can enable cooling certain modes independent of their detection and position in the spectrum, which may be promising for precision sensing applications.</p>
38

Ultracold Neutral Plasma Evolution in an External Magnetic Field

Pak, Chanhyun 26 June 2023 (has links) (PDF)
We study the expansion velocity and ion temperature evolution of ultracold neutral plasmas (UNPs) of calcium atoms under the influence of a uniform magnetic field that ranges up to 200 G. In the experiments, we use a magneto-optical trap (MOT) to capture the neutral atoms and laser-induced fluorescence (LIF) to take images of the plasma. We vary the magnetic field strengths and the initial electron temperatures and observe the plasma evolution in time. We compare the ion temperature evolution to the theory introduced in the paper by Pohl et. al. [Phys. Rev. A 70, 033416 (2004)]. The evolution of the gradient of expansion velocity suggests the presence of ion acoustic waves (IAWs). We speculate that our measurements showing that the ion temperature remains relatively high throughout the evolution is a biproduct of the IAW.
39

Microcombs for Timekeeping and RF Photonics

Nathan Patrick O'Malley (17053956) 27 September 2023 (has links)
<p dir="ltr">Optical frequency combs have revolutionized metrology and advanced other fields such as RF photonics and astronomy. While powerful, they can be bulky, expensive, and difficult to manufacture. This tends to limit uses in real-world scenarios. Within the last decade or so, coherent frequency combs have begun to be generated in millimeter-scale, CMOS fabrication-compatible nonlinear crystals. These so-called “microcombs” have led to hopes of overcoming deployability constraints of more traditional bulk combs.</p><p dir="ltr">One of the first applications for \textit{bulk} frequency combs after their explosion in 2000 was the optical atomic clock. It promised extreme long-term time stability better than that of the Cesium clock that currently defines the SI second. More recently, interest in a fully portable optical atomic clock has grown. Such a device could reliably keep time even without the aid of GPS references, and potentially with greater accuracy than current GPS synchronization can provide.</p><p dir="ltr">Frequency combs have also been used to sample electrical signals more rapidly than traditional electronics can accomplish. This has been used to achieve dramatically increased effective frequency bandwidths for signal detection architectures. One can imagine how this capability would be beneficial in a portable (microcomb-driven) form: a lightweight, comb-enhanced receiver able to capture a broadband snapshot of its surrounding electromagnetic environment could be a powerful tool.</p><p dir="ltr">Timekeeping and RF photonics are the primary applications of microcombs focused upon here. I will attempt to roughly summarize important concepts and highlight relevant work in both subjects in the Introduction. Then I will move a step closer to the hands-on lab work that has largely kept me preoccupied over the last several years and describe important or commonly-employed Methods for experiments. A collection of three journal manuscripts (two published, and the third recently submitted) will follow in the Publications chapter, highlighting some experimental results. Finally, I will conclude with a brief Outlook.</p>
40

Mélange à quatre ondes multiple pour le traitement tout-optique du signal dans les fibres optiques non linéaires / Multiple four wave mixing for all-optical signal processing in nonlinear optical fibers

Baillot, Maxime 15 December 2017 (has links)
Le mélange à quatre ondes est un effet non linéaire sensible à la phase qui suscite de nombreux intérêts dans le domaine de la génération de peignes de fréquences et du traitement tout optique du signal par exemple. Un peigne de fréquences peut en effet s'obtenir par effet de mélange à quatre ondes 1en cascade. Dans ce cas, un nombre N d'ondes interagissent entre elles via l'effet Kerr et la modélisation d'un tel processus doit tenir compte de tous les couplages possibles entre les ondes. Au cours de mes travaux de thèse, je me suis intéressé, dans un premier temps, à la modélisation du mélange à quatre ondes dit multiple pour lequel un nombre quelconque N d'ondes interagissent entre elles. J'ai proposé une formulation générale permettant d'identifier simplement tous les termes de mélange à quatre ondes issus de toutes les combinaisons possibles de couplage entre les ondes et leur désaccord de phase associé. J'ai validé cette approche en proposant une étude théorique et expérimentale d'un processus de mélange à quatre ondes multiple dans une fibre optique non linéaire. Dans une deuxième partie, j'ai proposé, grâce au modèle élaboré précédemment, une étude théorique du phénomène de conversion de fréquence sensible à la phase, permettant la décomposition des composantes en quadrature d'un signal optique. Dans la littérature, cette expérience fut démontrée initialement avec quatre ondes pompes et dans plusieurs types de composants non linéaires. J'ai pu démontrer, au cours de mes travaux, que trois pompes étaient suffisantes pour réaliser l'expérience et j'ai déterminé des relations analytiques simples permettant de choisir les paramètres expérimentaux (notamment l'amplitude et la phase des pompes) rendant possible la décomposition des composantes en quadrature d'un signal. J'ai validé cette étude par la démonstration expérimentale d'un convertisseur de fréquence sensible à la phase avec uniquement trois pompes et j'ai étudié théoriquement les effets de la dispersion chromatique sur les performances du convertisseur de fréquence. Enfin, dans une dernière partie, j'ai caractérisé des fibres optiques microstructurées en verre de chalcogénure fabriquées dans le cadre d'une collaboration avec Perfos, l'Institut des Sciences Chimiques de Rennes et SelenOptics. Dans ce cadre, j'ai mis en place un banc de mesure de la dispersion chromatique et du coefficient non linéaire des fibres optiques basé sur le mélange à quatre ondes. / Four-wave mixing is a phase-sensitive nonlinear effect that arouses interest, particularly in the fields of frequency comb generation and all-optical signal processing. As an example, frequency combs can be produced thanks to a cascaded four-wave mixing process. In this case, N waves can interact with each other through the optical Kerr effect, and one has to take into account all the possible interactions to be able to adequately model the process. During my PhD thesis, I was interested in modeling the so-called multiple four-wave mixing process, in which any number N of waves can interact with each other. I proposed a general formulation that allows to easily identify all the four-wave mixing terms originating from all the possible combinations of wave coupling and their associated phase-mismatch terms. I validated this approach through the theoretical and experimental study of a multiple four-wave mixing process in a nonlinear optical fiber. Thanks to the developed model, I then proposed a theoretical study of the phase-sensitive frequency conversion process, which permits to demultiplex the quadrature components of an optical signal. In the literature, this process was first experimentally demonstrated in several nonlinear devices using four pump waves. I demonstrated that only three pump waves were required to successfully perform the experiment, and I determined the simple analytical relations from which the adequate experimental parameters (namely, the amplitudes and phases of the pump waves) could be deduced. I finally validated this study by experimentally demonstrating a phase-sensitive frequency conversion process with only three pump waves, and I theoretically studied the influence of chromatic dispersion on the performance of this frequency converter. Finally, I characterized some chalcogenide microstructured optical fibers that were fabricated in the framework of a collaboration with Perfos, the Institut des Sciences Chimiques de Rennes, and SelenOptics. I set up a test bench based on the four-wave mixing process in order to measure the chromatic dispersion and nonlinear coefficient of some optical fibers.

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