Virgo est un interféromètre de Michelson dont les bras contiennent des cavités Fabry-Perot. Il a été construit pour détecter directement les ondes gravitationnelles. Le projet Advanced Virgo est une amélioration majeure de Virgo pour atteindre une sensibilité encore plus élevée avec laquelle la détection des ondes gravitationnelles deviendra probable. On prévoit un système laser mono-fréquence de 175 Watts de puissance optique présentant des stabilités accrues pour le bruit relatif de puissance et pour le bruit de fréquence. Ce travail de thèse a pour objet la réalisation de ce système laser de haute-puissance et de haute-stabilité basée sur l'utilisation d'amplificateurs à fibre combinés de façon cohérente. Des amplificateurs à fibre disponibles dans le commerce sont caractérisés en termes de qualité de faisceau, de bruit de puissance, de bruit de fréquence, de stabilité de pointé du faisceau, et également en terme de stabilité à long terme sur quelques milliers d'heures. On implémente l'interférométrie de Mach-Zehnder pour la combinaison cohérente de faisceaux. Les techniques de caractérisation de faisceaux laser sont aussi développées en considérant leurs limites ultimes. Hormis un déficit de puissance optique, le système laser développé dans cette étude sur la base de la combinaison cohérente de Master Oscillator Fiber Power Amplifiers, remplit les conditions posées par Advanced Virgo. / Virgo is a cavity-enhanced Michelson interferometer built for the direct detection of gravitational waves. The Advanced Virgo project consists of major upgrades to the Virgo gravitational wave detector for an order of magnitude improvement in differential strain sensitivity, one of which is the tenfold increase in injected laser power to 175 Watts. The use of fiber laser amplifiers and their coherent combination are foreseen to deliver the required high-power low-noise beam. In this thesis work, we review the laser requirements for gravitational wave detectors, introduce the design of the laser system for Advanced Virgo, and develop the means for laser characterization in accordance with the stringent noise specifications. We then present the results to date, notably the quasi-continuous long-term operation of two 40-Watt fiber laser amplifiers over thousands of hours and their coherent combination with Mach-Zehnder interferometry. Although the targeted power for Advanced Virgo is not yet attained, the developed system shows decent noise performance and is promising for further power-scaling efforts.

La diffusion Brillouin est la diffusion inélastique de la lumière par les ondes acoustiques d'un milieu. Dans une fibre optique, la diffusion Brillouin stimulée (DBS) se manifeste, à partir d'une certaine intensité lumineuse incidente (Pompe), par la génération d'une onde Stokes rétrodiffusée dont la fréquence est décalée de celle de la Pompe d'une valeur directement proportionnelle à la vitesse de propagation des ondes acoustiques. Le décalage Brillouin présente une grande sensibilité à tous les effets qui peuvent modifier la vitesse de l'onde acoustique. Cette propriété permet d'étudier la composition des fibres et confère à la DBS la potentialité pour la réalisation de capteurs à fibres optiques. Le processus de DBS s'accompagne aussi d'un gain pour l'onde Stokes rétrodiffusée, puisque presque toute la puissance de l'onde Pompe y est transférée. Il peut donc être utilisé pour la réalisation d'amplificateurs et de lasers à fibres optiques. Dans le cadre de ce travail de thèse, nous avons étudié expérimentalement les propriétés statiques et dynamiques du laser à fibre Brillouin (LFB). Dépendamment du taux d'amortissement de l'onde acoustique et du taux de pertes de la cavité, le LFB peut être très cohérent et très peu bruité, favorisant ainsi son utilisation dans de multiples domaines comme la défense, la métrologie et les télécommunications. Lorsque la Pompe ne fait qu'un tour dans la cavité Brillouin, le LFB étudié présente un bruit de fréquence 10 000 fois plus faible que celui du laser de Pompe tout en gardant un bruit d'intensité similaire. Lorsque la Pompe est résonante, il est possible d'obtenir un LFB à multiples ondes Stokes en cascadant l'effet non-linéaire Brillouin dans la fibre optique. Limités par nos bancs de mesures, nous avons mesuré un bruit de fréquence 1 000 fois plus faible que celui de la Pompe et un bruit d'intensité plus de 100 fois plus faible. / Brillouin scattering is the inelastic scattering of light by the acoustic waves of a medium. In an optical fiber, stimulated Brillouin scattering occurs, from a certain incident light intensity (pump), for generating a backscattered "Stokes" wave, whose frequency is shifted from that of the pump by a value directly proportional to the acoustic wave propagation velocity in the fiber. The Brillouin shift has a high sensitivity to all effects that can change the speed of the acoustic wave. This property makes it possible to study the composition of the fibers and gives to the SBS the potential for the production of optical fiber sensors. The SBS process is also accompanied by a gain for the backscattered Stokes wave since almost all the power of the Pump wave is transferred there. It can, therefore, be used for the production of optical fiber amplifiers and lasers. As part of this thesis work, we experimentally studied static and dynamic properties of the Brillouin fiber lasers (BFLs). Depending on the damping rate of the acoustic wave and the loss rate of the cavity, the BFL can be very coherent and less noisy, thus promoting its use in multiple fields such as defense, metrology, and telecommunications. When the Pump makes only one turn in the Brillouin cavity, the studied BFL has a frequency noise 10,000 times lower than that of the Pump laser while keeping a similar intensity noise. When the Pump is resonant, it is possible to obtain a BFL with multiple Stokes waves by cascading the Brillouin non-linear effect in the optical fiber. Restricted by our measurement benches, we measured a frequency noise 1000 times lower than that of the Pump and an intensity noise more than 100 times lower.

Ce travail de thèse porte sur l'étude de la faisabilité d'un capteur d'ondes acoustiques à base de laser à fibre. Cet hydrophone doit permettre la détection de faibles fluctuations de pression hydrostatique rencontrées à des grandes profondeurs marines. Sous l'influence d'une perturbation acoustique le laser est étiré; ce qui change le pas du réseau de Bragg et ainsi sa fréquence d'émission. L'information est donc codée dans la fréquence de la lumière émise. Le bruit de fréquence intrinsèque du laser doit alors être le plus bas possible d'où l'importance de pouvoir le mesurer dans la bande de fréquence [DC-20kHz]. Ainsi, nous effectuons une étude approfondie des propriétés physiques de l'émission laser en terme de cohérence temporelle. La sensibilité d'un laser à fibre à la pression acoustique est insuffisante. Il est primordial de concevoir un amplificateur mécanique qui permettra d'augmenter le rapport signal sur bruit du capteur. / This thesis focuses on the study of the feasibility of an acoustic wave sensor based on fiber laser. This hydrophone should allow the detection of low hydrostatic pressure fluctuations encountered in deep marine. Under the influence of an acoustic disturbance is stretched the laser; thereby changing the pitch of the Bragg grating and thus its transmission frequency. The information is coded in the frequency of the emitted light. The intrinsic frequency noise of the laser must be as low as possible so it is important to be able to measure in the frequency band of $[DC-20KHz]$. Thus we conduct a thorough study of the physical properties of the laser emission in terms of temporal coherence.The sensitivity of a fiber laser acoustic pressure is insufficient. It is essential to design a mechanical amplifier for to increase the signal to noise ratio of the sensor.

This diploma thesis is divided into two main parts. The first section is dedicated to the history and development of the laser technology. The second part describes all individual types of laser technology which are used in the industry nowadays. The next section follows with the research of various laser devices which serve mainly as a cutting tool. This knowledge gathered in the previous part was used to create the next part including the own conception of the machine. The second half of this diploma thesis deals with a research of software available at the market today. Eventually, after summarizing the characteristics of each software, the new concept and implementation of own software are made. In the final section, there are mentioned the possible extension and available upgrades. The reader should be able to create his/her own conception of the laser device and software after reading and understanding this paper.

This diploma thesis is divided into two main parts. The first section is dedicated to the history and development of the laser technology. The second part describes all individual types of laser technology which are used in the industry nowadays. The next section follows with the research of various laser devices which serve mainly as a cutting tool. This knowledge gathered in the previous part was used to create the next part including the own conception of the machine. The second half of this diploma thesis deals with a research of software available at the market today. Eventually, after summarizing the characteristics of each software, the new concept and implementation of own software are made. In the final section, there are mentioned the possible extension and available upgrades. The reader should be able to create his/her own conception of the laser device and software after reading and understanding this paper.

This thesis deals with research of cutting defects at laser cutting of 15 mm thick carbon steel by Bystronic fiber laser with emphasis on wide cutting gap, which causes enlargement of wide of cutting gap and deterioration of roughness of cutting edge and increase of creation fo heat. The introduction describes the main types of lasers used for cutting sheet of metal and compare their advantages and disadvantages. Also described is a cutting process and its parameters, and also the possible cutting defects. An experiment was conducted on steels S355MC and S235JR and cutting defects were analyzed in relation to the set of cutting parameters. Next part determines the extent of the recommended parameters that should be chosen for specific cutting conditions and is balanced recommendations regarding the choice of material to be cut, and technological adaptations parts. In the last part is measured roughness of a wide cutting gap, the width of the heat affected zone and micro-hardness of the material.

<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>

[pt] Um dos maiores desafios na perfuração das rochas carbonáticas, situadas a grandes profundidades, é superar as baixas taxas de penetração que vem sendo obtidas na perfuração de poços verticais e direcionais. Para vencer este desafio, um grande esforço vem sendo desenvolvido em várias linhas de pesquisa, tanto no desenvolvimento de novos conceitos de brocas como na seleção de um sistema de perfuração que apresente um melhor desempenho. Para atingir este objetivo, estão sendo priorizados procedimentos e sistemas de perfuração que apresentem menores níveis de vibração, pois este fenômeno além de reduzir a eficiência da perfuração, também compromete o tempo de vida útil dos equipamentos e, por consequência, acarreta a redução da confiabilidade do sistema e eleva o custo por metro da perfuração. Por conseguinte, novas tecnologias de brocas e sistemas de perfuração estão em desenvolvimento e, dentre as novas tecnologias, podemos diferenciar aquelas que promovem melhorias nas tecnologias convencionais e as tecnologias francamente inovadoras, aquelas que utilizam novos mecanismos para cortar ou fragilizar a rocha. Dentre as tecnologias inovadoras, a perfuração assistida por laser é uma das mais promissoras, nesta versão o feixe da energia radiante tem a função principal de fragilizar a rocha, facilitando o avanço da perfuração. Esta dissertação tem por objetivo realizar uma avaliação das possibilidades de aplicação da tecnologia laser na perfuração de rochas. O meio através do qual o laser deverá atuar nas aplicações futuras é analisado sobre o enfoque das suas propriedades físico-químicas. Dessa forma, o conhecimento da interação com o fluido de perfuração é o ponto de partida para a análise de viabilidade. Inicialmente, análises de absorção ótica foram realizadas em alguns tipos de fluido utilizados na indústria do petróleo e, na sequência, foram realizados testes de bancada com um dispositivo eletro-mecânico, especialmente desenvolvido, para servir de base para o laser, com potência máxima de 1500 W, direcionado sobre amostras de rochas carbonáticas. A análise de absorção ótica tem por objetivo compreender melhor o processo de interação do laser com o fluido de perfuração. Os testes de absorção ótica foram realizados para avaliar a absorção da luz, na faixa de comprimento de onda entre 800 nm até 1200 nm. A partir destas informações foi dado o primeiro passo no conhecimento da interação com o fluido de perfuração. Na seqüência da abordagem, um resumo, em nível de pesquisa bibliográfica é apresentado com os estudos, análises e testes de bancada já realizados por vários pesquisadores para verificar o estágio de desenvolvimento desta tecnologia inovadora. A partir deste conhecimento, será possível fazer uma inferência sobre as reais possibilidades desta tecnologia e iniciar um levantamento preliminar sobre os pontos considerados críticos para a sua aplicação, no cenário de perfuração de um poço de petróleo. O cenário de perfuração, como se sabe, é um ambiente agressivo, sujeito a altas vibrações, temperaturas e pressões elevadas. Para concluir, serão apresentados os resultados obtidos em teste de bancada com dispositivo especificamente construído para a fundamentação das conclusões da dissertação. Dentre os aspectos mais relevantes, podemos mencionar: a determinação da durabilidade do sistema, considerando a resistência da lente de focalização ao aquecimento provocado pelo laser e, também, uma avaliação da eficiência do processo sob o ponto de vista do valor obtido para a energia específica. Em resumo, o objetivo final dessa dissertação é o de concentrar em um documento as informações mais atualizadas sobre a utilização do laser na perfuração de rochas e apresentar uma análise, ainda que preliminar, sobre os possíveis pontos de melhoria que permitam viabilizar esta tecnologia no futuro. / [en] One of the biggest challenges in drilling the carbonate rocks located at great depths is to overcome low penetration drilling rates that have been obtained in vertical and directional wells. To overcome this challenge, a great effort is being developed on multiple lines of research. All of them are focused in new concepts of drilling procedures and the selection of a drilling system that presents a better performance. To achieve this goal, new procedures are being designed and drilling systems with lower vibration levels are under development. Vibration reduces the efficiency of drilling, also decreases the lifetime of equipment and consequently causes a reduction in reliability of all system and raises the drilling costs. Consequently, new drill bit technologies and drilling systems are being developed and, among the new technologies we can differentiate those that only promote improvements in conventional technologies and those innovative technologies, in which new mechanisms to cut or weaken the rock are used. The drilling assisted laser is one of the most promising mechanism in which the radiant energy beam has the primary function to weaken the rock increasing the performance of drilling process. This dissertation aims to perform an assessment of the possibilities of laser technology in rock drilling applications. The laser will have to pass through the drilling fluid in the future applications so it is very important to understand their physicochemical properties and their mutual interaction. For this reason, the knowledge of the interaction with the drilling fluid is the starting point for this work. First of all, it will be accomplished an analysis of optical absorption in some types of fluid used in the oil industry. After that, it will be performed bench testing with an electro-mechanical device that will support a laser whose maximum power can reach 1500 W and it will be pointed to carbonate rock samples. The optical absorption analysis aims to better understand the interaction of the laser with the drilling fluid. The optical absorption tests are performed to evaluate the absorption of light in the wavelength range from 800 nm to 1200 nm. From this information, it will be taken the first step to understand the interaction with the drilling fluid, which is the starting point for the feasibility study of the use of lasers. Following the approach, a literature review will be presented with the studies, analysis and bench testing already conducted by various researchers to check the stage of development of this new technology. Taking into account this knowledge, it will be possible to make an initial approach about the actual possibilities of this technology and initiate a preliminary survey on the questions that are critical to its application in a drilling scenario in the well construction, an aggressive environment which is subject to high vibrations, high temperatures and pressures. To conclude, we present the results obtained in bench testing with device specifically built for supporting the conclusions of the dissertation. Among the most relevant aspects, we can mention the durability of the system, considering the focusing lens lifetime under the heating effects caused by the laser. Another point, it is to make an evaluation of the performance of drilling process, considering the specific energy. In summary, the ultimate goal of this dissertation is to concentrate in a single document the most current information about the use of laser drilling and present an analysis, though preliminary, about the possible improvement points that will allow the feasibility of this technology in the future.

Metal surface cleaning is highly required in different fields of modern industry. Nuclear industry seeks for new methods for oxidized surface decontamination, and thermonuclear installations require the cleaning of plasma facing components from tritium-containing deposited layer. The laser ablation is proposed as an effective and safe method for metal surface cleaning and decontamination. The important factor influencing the laser heating and ablation is the in-depth distribution of laser radiation. The model of light propagation in a scattering layer on a metal substrate is developed and applied to analyse the features of light distribution. To simulate the contaminated surfaces, the stainless steel AISI 304L was oxidized by laser and in a furnace. Radioactive contamination of the oxide layer was simulated by introducing europium and/or sodium. The decontamination factor of more than 300 was demonstrated with found optimal cleaning regime. The decreasing of the corrosion resistance was found after laser cleaning. The ablation thresholds of ITER-like surfaces were measured. The cleaning productivity of 0.07 m2/hour∙W was found. For mirror surfaces, the damage thresholds were determined to avoid damage during laser cleaning. The possibility to restore reflectivity after thin carbon layer deposition was demonstrated. The perspectives of further development of laser cleaning are discussed.

Les lasers à fibres à modes bloqués font partie des rares systèmes qui permettent de réaliser une variété de fonctions optiques élaborées, au moyen de peu de composants optiques. La gestion de la dispersion apporte à ce type de lasers une variété de comportements, qui est si riche que la cartographie complète et l’analyse détaillée des états stables deviennent difficilement réalisable lorsqu’on utilise les outils conventionnels basés sur les équations de propagation du champ intra-cavité. Dans cette thèse nous montrons que l’adjonction de la technique des coordonnées collectives aux outils théoriques conventionnels, permet de résoudre au moins en partie le problème de la complexité et l’extrême diversité des états stables des cavités gérées en dispersion. En particulier, nous proposons l’ACCD (approche des coordonnées collectives dynamiques), comme un outil théorique permettant de réaliser des gains de performance substantiels dans des opérations de recherche et caractérisation des états stables du laser. D’autre part, le recours à l’approche des cordonnées collectives nous permet de mettre en évidence des effets majeurs induits par certains phénomènes qui étaient jusqu’à présent largement sous-estimés. Notamment, nous mettons en évidence des modifications majeures desdomaines respectifs des différents états stables du laser, qui surviennent lorsqu’on change la bande passant de la fitre. D’autre part, en considérant une cavité où la largeur spectrale du champ lumineux (3.12 THz) est d’un ordre de grandeur plus petite que la largeur de la bande du gain Raman, nous mettons en lumière des effets remarquables de la diffusion Raman sur les phénomènes d’hystérésis. / Mode-locked fiber laser are among the few systems that allow to achieve a variety of elaborate optical functions, by means of few optical components. The use of dispersion management brings to this type of lasers a variety of behaviors, which is so rich that the complete mapping and detailed analysis of the stable states becomes impractical when conventional tools based on the intra-cavity field propagation equations, are used. In this thesis we show that the addition of the technique ofcollective coordinates to the conventional theoretical tools, allows to solve at least in part the problem of complexity and diversity of the stable states of the cavity. In particular, we propose the DCCA (dynamical collective coordinate approach), as a theoretical tool to achieve substantial performance gains in search and characterization of stable states of the laser. Furthermore, the use of the collective coordinated approach allows us to highlight major effects induced by certain phenomena that were until now largely underestimated. In particular, we highlight major changes in the respective areas ofthe different stable states of the laser, which occur when changing the width of the band-pass filter BPF. Furthermore, considering a cavity where the spectral width of the light field (3.12 THz) is an order of magnitude smaller than the bandwidth of the Raman gain, we highlight remarkable effects of Raman scattering on hysteresis phenomena.