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Meseguer, Brocal Gabriel. "Multimodal analysis : informed content estimation and audio source separation". Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS111.
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Cette thèse propose l'étude de l'apprentissage multimodal dans le contexte de signaux musicaux. Tout au long de ce manuscrit, nous nous concentrerons sur l'interaction entre les signaux audio et les informations textuelles. Parmi les nombreuses sources de texte liées à la musique qui peuvent être utilisées (par exemple les critiques, les métadonnées ou les commentaires des réseaux sociaux), nous nous concentrerons sur les paroles. La voix chantée relie directement le signal audio et les informations textuelles d'une manière unique, combinant mélodie et paroles où une dimension linguistique complète l'abstraction des instruments de musique. Notre étude se focalise sur l'interaction audio et paroles pour cibler la séparation de sources et l'estimation de contenu informé. Les stimuli du monde réel sont produits par des phénomènes complexes et leur interaction constante dans divers domaines. Notre compréhension apprend des abstractions utiles qui fusionnent différentes modalités en une représentation conjointe. L'apprentissage multimodal décrit des méthodes qui analysent les phénomènes de différentes modalités et leur interaction afin de s'attaquer à des tâches complexes. Il en résulte des représentations meilleures et plus riches qui améliorent les performances des méthodes d'apprentissage automatique actuelles. Pour développer notre analyse multimodale, nous devons d'abord remédier au manque de données contenant une voix chantée avec des paroles alignées. Ces données sont obligatoires pour développer nos idées. Par conséquent, nous étudierons comment créer une telle base de données en exploitant automatiquement les ressources du World Wide Web. La création de ce type de base de données est un défi en soi qui soulève de nombreuses questions de recherche. Nous travaillons constamment avec le paradoxe classique de la `` poule ou de l'œuf '': l'acquisition et le nettoyage de ces données nécessitent des modèles précis, mais il est difficile de former des modèles sans données. Nous proposons d'utiliser le paradigme enseignant-élève pour développer une méthode où la création de bases de données et l'apprentissage de modèles ne sont pas considérés comme des tâches indépendantes mais plutôt comme des efforts complémentaires. Dans ce processus, les paroles et les annotations non-expertes de karaoké décrivent les paroles comme une séquence de notes alignées sur le temps avec leurs informations textuelles associées. Nous lions ensuite chaque annotation à l'audio correct et alignons globalement les annotations dessusThis dissertation proposes the study of multimodal learning in the context of musical signals. Throughout, we focus on the interaction between audio signals and text information. Among the many text sources related to music that can be used (e.g. reviews, metadata, or social network feedback), we concentrate on lyrics. The singing voice directly connects the audio signal and the text information in a unique way, combining melody and lyrics where a linguistic dimension complements the abstraction of musical instruments. Our study focuses on the audio and lyrics interaction for targeting source separation and informed content estimation. Real-world stimuli are produced by complex phenomena and their constant interaction in various domains. Our understanding learns useful abstractions that fuse different modalities into a joint representation. Multimodal learning describes methods that analyse phenomena from different modalities and their interaction in order to tackle complex tasks. This results in better and richer representations that improve the performance of the current machine learning methods. To develop our multimodal analysis, we need first to address the lack of data containing singing voice with aligned lyrics. This data is mandatory to develop our ideas. Therefore, we investigate how to create such a dataset automatically leveraging resources from the World Wide Web. Creating this type of dataset is a challenge in itself that raises many research questions. We are constantly working with the classic ``chicken or the egg'' problem: acquiring and cleaning this data requires accurate models, but it is difficult to train models without data. We propose to use the teacher-student paradigm to develop a method where dataset creation and model learning are not seen as independent tasks but rather as complementary efforts. In this process, non-expert karaoke time-aligned lyrics and notes describe the lyrics as a sequence of time-aligned notes with their associated textual information. We then link each annotation to the correct audio and globally align the annotations to it. For this purpose, we use the normalized cross-correlation between the voice annotation sequence and the singing voice probability vector automatically, which is obtained using a deep convolutional neural network. Using the collected data we progressively improve that model. Every time we have an improved version, we can in turn correct and enhance the data
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Laurain, Alexandre. "Sources laser à semiconducteur à émission verticale de haute cohérence et de forte puissance dans le proche et le moyen infrarouge". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2010. http://tel.archives-ouvertes.fr/tel-00613743.
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Le développement de sources lasers monomodes et accordables constitue un enjeu important dans plusieurs domaines en fort développement telle que la métrologie, les senseurs optiques, la spectroscopie, le traitement optique de l'information ou la médecine. Dans cette thèse nous faisons le point sur les limites des technologies actuelles, puis nous montrons comment les surpasser à travers la conception et l'étude physique de lasers à semiconducteur de haute cohérence émettant dans l'infrarouge. Nous nous intéressons particulièrement aux VECSEL dans le but d'obtenir un fonctionnement monofréquence accordables et robustes. Nous traitons de la conception et de la caractérisation de ces lasers, depuis l'optimisation du milieu à gain jusqu'à l'élaboration de prototypes laser fonctionnels. Nous effectuons ensuite une étude approfondie des propriétés physiques de la source. Les différents sujets abordés traitent de nombreux aspects de l'optoélectronique tels que la physique du solide, l'optique traditionnelle et quantique, la technologie des matériaux, la thermique, ect. Les travaux présentés ici ouvrent la voie à de nombreux développements liés aux VECSEL et à leurs applications.
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Rame, Jérémy. "Recherche et élaboration de nouveaux matériaux pour les applications laser non-linéaires du moyen infrarouge". Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066716.
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Le moyen infrarouge (MIR) présente un fort intérêt technologique du fait de la présence de bandes de transparence de l’atmosphère dans ce domaine. En effet, elles permettent d’envisager de nombreuses applications à longue distance, telles que la détection de gaz ou le brouillage infrarouge de missiles pour la sécurité des aéronefs civils ou militaires. Les sources paramétriques optiques font partie des technologies de choix pour la génération d’impulsions laser dans ce domaine. Elles nécessitent l’emploi de cristaux non-linéaires pour convertir des signaux laser, du proche infrarouge vers le MIR, dont un état de l’art est présenté dans cette étude. AgGaGeS4 est un candidat prometteur pour ces applications. L’élaboration de ce matériau par la technique de synthèse chimique double zone et la cristallogenèse par la technique Bridgman-Stockbarger est ici présentée. Des lingots d’AgGaGeS4 (φ=28 mm et L=70 mm) ont pu être obtenus. Les facteurs clés pour le développement de ces cristaux ont été mis en évidence, en particulier le contrôle de la volatilité du GeS2. Par ailleurs, un dispositif permettant d’améliorer la méthode de synthèse chimique, en mesurant en temps réel les variations de pression au cours du procédé, est proposé. Concernant ZnGeP2, matériau de référence dans ce domaine, des simulations ab initio ont été réalisées pour étudier l’influence de substitutions ioniques sur les propriétés de ce composé. En complément, des monocristaux de ZGP:Sn ont été élaborés et caractérisés. L’ajout d’étain a permis d’améliorer significativement la transmission optique vers 2 μm, longueur d’onde de pompage de ce cristalMid-infrared laser sources have attracted a particular attention due to their potential applications in different fields, such as remote chemical sensing or infrared counter-measures for civilian or military aircrafts safety. One way to produce such sources is the down conversion process in optical parametric oscillators using nonlinear crystals. AgGaGeS4 is a promising candidate for these applications. The chemical synthesis and crystal growth steps of this material processing are presented in this study. Ingots with 28 mm diameter and 70 mm length were grown. The key issue of AgGaGeS4 processing is the control of melt decomposition at high temperature due to the high volatility of GeS2. The influence of GeS2 volatility on melt stoichiometry during the AgGaGeS4 processing is outlined, and solutions to improve crystals quality by controlling this volatility are presented. Otherwise, we present the development of a device which aim to improve the chemical synthesis process by controlling the pressure variations during the chemical reaction. Main interests of this device are to study the chemical reaction which occurs during the process and control the pressure variations during the chemical reaction. Furthermore, ab initio calculations were performed in order to study the properties of ZnGeP2 which is a benchmark material for mid-IR laser conversion. The effect of ionic substitution on ZnGeP2 properties was studied. Moreover, ZnGeP2:Sn crystals were elaborated and characterized. It was demonstrated that ionic substitutions with tin allowed significantly improvements on the crystal transmission around the pump wavelength at 2.05 μm
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Dury, Martin. "Development of the NPL wide-area MIR calibration source". Thesis, University of Reading, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555860.
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A portable large area specular-diffuse secondary radiance transfer standard developed for the in-field calibration of remote sensing instrumentation for hot gas emission spectroscopy was designed, produced and characterised to a limited budget. The cavity has an aperture diameter of 102 mm was designed to have a known spectral radiance with a 1 % uncertainty in the 2.5 urn to 14 μm wavelength range. The prototype cavity is based around a grooved base that is electrically heated to temperatures up to 1000 K. The base has been applied with a high emittance coating, which was selected after extensive testing and does not deteriorate after repeated heating. Highly reflective walls surround the emitting base and are water-cooled. '. Coating selection was determined through reflectance measurements of both highly emitting and highly reflective coatings that were performed across the spectral range from 0.3 μm to 14 μm. The reflectance data was subsequently input into black body modelling software and Monte Carlo calculations were performed to optimise the design of the cavity. Problems regarding the heating elements within the emitting base lead to the development of a cost effective solution. Characterisation of the cavity was performed at a wavelength of 800 nm using filter radiometers. Large temperature discrepancies were observed across the cavity aperture and a correction factor was implemented to determine the temperature distribution across the cavity. The temperature distributions were input into black body modelling software and the cavity performance simulated. Radiance measurements of the cavity were performed using an FTIR spectrometer and the cavity emissivity determined to be 0.98 (±0.04) in the wavelength interval from 3.64 to 3.65 μm (the wavenumber interval from 2747 cm-I to 2740 cm").
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Liu, Miaomiao. "Actinomycetes Sourced From Unique Environments as a Promising Source of New TB-Active Natural Products". Thesis, Griffith University, 2017. http://hdl.handle.net/10072/366523.
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Tuberculosis (TB) is the leading cause of death from infectious diseases in the world, affecting more than ten million patients each year. However, multi-drug resistance (MDR-TB) threatens progress achieved in TB care and control, and there are few drugs available to treat MDR-TB. Our overall aim was to identify anti-TB natural products from microbes sourced from unique environments. This thesis presents efforts to achieve an effective approach to identify anti-TB microbial natural products with the combination of one strain many compounds (OSMAC) strategy, NMR fingerprint and principal component analysis.
The thesis begins with an introduction of TB and the current anti-TB drugs and candidates. It also covers a review on anti-TB natural products from marine microbe and endophyte origin and analysis of their physicochemical properties using Lipinski’s rule of five as well as the ChemGPS tool. As part of a research program aiming to identify anti-TB microbial constituents, a cell-based screening assay was developed to screen 2562 crude extracts. Among the active hits, 46 actinomyces isolated from marine, desert or
Traditional Chinese Medicines were selected for further chemical investigation according to their chemical profiles or anti-TB activities. The results are presented in chapters 2 to 7.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
Full Text
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Mörz, Florian [Verfasser]. "Ultrafast laser sources : tunable, ultrafast laser sources for near- and mid-IR spectroscopy / Florian Mörz". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1222515504/34.
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Wei, Junxiong. "Novel nonlinear frequency conversion sources in the mid-infrared". Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/664929.
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The goal of this thesis has been the development of a new class of advanced solid-state photonic sources for the mid-infrared (mid-IR) spectral regions, where there exists a severe shortage of practical coherent laser sources, and many scientific and technological applications can benefit. The strategy has been to exploit nonlinear optical techniques based on difference frequency generation (DFG), parametric generation and oscillation, in the latest class of mid-IR nonlinear materials, in combination with the most advanced lasers pump sources based on fiber laser technology, to realize novel, high-power coherent source with broad tunability in the mid-IR.
Accordingly, we demonstrate an angle-tuned MgO:PPLN picosecond OPO, synchronously pumped by a Yb-fiber laser, for the first time to the best of our knowledge. The OPO is tunable from 1413-1900 nm in the signal togerther with idler tunability across 2418-4307 nm providing a total tunability of 2376 nm in the near-to-mid-IR region, simply by angular interrogation of the MgO:PPLN crystal at room temperature. Using a 10% output coupler, we were able to extract up to 2.4 W of signal at 1664 nm together with an idler power of 1.7 W at 2950 nm, corresponding to an overall extraction efficiency of ~45% with good beam pointing stability of better than 30 µrad and 14 µrad for the signal and idler, respectively. These results indicate the potential for rapid and wide tunability of high-power OPOs as compared to the temperature tuned devices.
In addition, we have demonstrated a novel device based on a tandem configuration, for an injection-seeded pulsed OPO system. Using a 38-mm-long PPLN crystal, we have produced ~0.94 W of average power with 9.7% slope efficiency at 1677 nm, for a pump power of 10 W at 80 kHz repetition rate. The measured optical bandwidth of signal is less than 20 MHz, and the seeding operation is achieved over signal wavelengths ranging from 1510 to 1677 nm, providing a total seeding range of 167 nm in the near-IR region. From a more general viewpoint, the method shownhere will also work at other wavelength range of OPO as well, opening a new path towards injection-seeding or injection-locking of pulse OPOs with full tuning range and high spectral purity.
Finally, we present detailed characterization of optical properties of the recently developed nonlinear material, orientation-patterned gallium phosphide (OP-GaP), by performing DFG experiments in the 2492-2782 nm wavelength range in the mid-IR. Detrimental issues such as thermal effects and residual absorption have been studied and confirmed by performing relevant measurements. Temperature and spectral acceptance bandwidths for DFG in the 40-mm-long OP-GaP crystal have been measured to be 18 ºC and 4 nm, respectively, at 1766 nm. Further, we have measured the damage threshold of the OP-GaP crystal to be 0.8 J/cm2 at 1064 nm, for the first time. The polarization dependence of the input beams on the DFG power has also been systematically investigated. To our knowledge, this is the first report on tunable DFG in OP-GaP, as well as the first nanosecond DFG source based on this new nonlinear materialEl objetivo de esta tesis era el desarrollo de una nueva clase de fuentes fotónicas de estado sólido para las regiones espectrales del infrarrojo medio (mid-IR), donde existe una gran escasez de fuentes láser coherentes, que pueden ser utilizadas para muchas aplicaciones científicas y tecnológicas. La estrategia consistió en explotar técnicas de óptica no lineal basadas en la generación de frecuencias diferencia (DFG), la generación paramétrica y la oscilación óptica paramétrica, usando la nuevos materiales no lineales para el mid-IR, en combinación con las fuentes de bombeo láser más avanzadas basadas en la tecnología láser de fibra, para realizar nuevas fuentes coherentes de alta potencia y amplia sintonía en el mid-IR. Esta tesis presenta dispositivos de oscilación óptica paramétrica (OPO) usando novedosos diseños, basados en materiales de quasi-phase-matching (QPM) y utilizando nuevos conceptos para facilitar la accesibilidad a la longitud de onda desde 1 μm en la región cercana al infrarrojo cercano hasta la región del mid-IR. En consecuencia, demostramos un OPO de picosegundo con sintonización por ángulo del cristal MgO:PPLN, bombeando sincrónicamente por un láser de fibra de Yb, por primera vez según nuestro conocimiento. El OPO es sintonizable de 1413-1900 nm en el signal juntamente con la sintonización del idler a través de 2418-4307 nm que proporciona una sintonización total de 2376 nm en la región del infrarojo-cercano y mid-IR, simplemente por la interrogación angular del cristal de MgO:PPLN en temperatura ambiente. Utilizando un acoplador de salida del 10%, pudimos extraer hasta 2,4 W de señal a 1664 nm junto con una potencia de idler de 1,7 W a 2950 nm, lo que corresponde a una eficiencia total de extracción de ~45% con una buena estabilidad de apuntamiento del haz mejor que 30 μrad y 14 μrad para el signal y el idler, respectivamente. Estos resultados indican el potencial para una rápida y amplia sintonización de OPOs de alta potencia en comparación con los dispositivos sintonizados por temperatura. Además, demostramos un novedoso dispositivo basado en una configuración en tándem, para un sistema OPO pulsado con un sistema "injection-seeded". Utilizando un cristal PPLN de 38 mm de longitud, hemos producido ~0,94 W de potencia media con una eficiencia de pendiente del 9,7% a 1677 nm, para una potencia de bombeo de 10 W a una tasa de repetición de 80 kHz. La anchura de banda óptica de la señal medida es inferior a 20 MHz, y la operación de "seeding" se realiza en longitudes de onda de la señal que oscilan entre 1510 y 1677 nm, lo que proporciona una gama total de "seeding" de 167 nm en la región cercana al infrarrojo-cercano. Desde un punto de vista más general, el método mostrado aquí también funcionará en otros rangos de longitud de onda de OPO, abriendo un nuevo camino hacia el "seeding" por inyección o el bloqueo por inyección de OPOs de pulso con rango de sintonía completo y alta pureza espectral. Por último, presentamos una caracterización detallada de las propiedades ópticas del material no lineal recientemente desarrollado, el orientation-patterned gallium phosphide (OP-GaP), mediante la realización de experimentos de DFG en el rango de longitud de onda de 2492-2782 nm en el rango de infrarrojos medio. Se han estudiado y confirmado cuestiones perjudiciales como los efectos térmicos y la absorción residual mediante la realización de las mediciones pertinentes. La temperatura y las anchuras de banda de aceptación espectral para DFG en el cristal OP-GaP de 40 mm de longitud han sido medidas obteniendo 18 ºC y 4 nm, respectivamente, a 1766 nm. Además, por primera vez hemos medido el umbral de daño del cristal OP-GaP siendo de 0,8 J/cm2 a 1064 nm. También se ha investigado sistemáticamente la dependencia de la polarización de los haces de entrada con respecto a la potencia de la DFG. Hasta donde sabemos, este es el primer informe sobre DFG sintonizable en OP-GaP, así como la primera fuente de nanosegundos DFG basada en este nuevo material no lineal.
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Nshii, Chidi Christopher. "Tunable mid-infrared light sources based on intersubband transitions". Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2603/.
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This thesis describes how for the first time, unidirectional operation and coupled ring tuning were realised on a quantum cascade laser material; specifically on a new strain compensated In0.7Ga0.3As/AlAs0.6Sb0.4 grown on InP substrate and operates in pulsed mode in the 3-4 micron hydrocarbon absorption region. Unidirectional ring lasers have the advantages that, in the favoured emission direction, they can have up to double the quantum efficiency of bidirectional lasers and do not suffer from spatial hole burning. In this work, this operation was realised by incorporating an "S"-crossover waveguide into the ring cavity in a manner that it introduces non reciprocal loss and gain in the counter-clockwise (CCW) and clockwise (CW) directions respectively. The measured result showed higher quantum efficiency in the CW. In fact at 1.5 times the threshold current, 90 % of the light was emitted in the favoured CW. On the other hand, the coupled ring quantum cascade laser showed nearly single mode operation, with side mode suppression ratio ~22 dB. Continuous wavelength tuning of about 13 nm was observed from one of these devices, at a tuning rate of approximately 0.4 nm/mA.
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Cook, James Matthew. "Mid-fifteenth-century English mass cycles in continental sources". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/30778/.
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Fifteenth-century English music had a profound impact on mainland Europe, with several important innovations (e.g. the cyclic cantus firmus Mass) credited as English in origin. However, the turbulent history of the Church in England has left few English sources for this deeply influential repertory. The developing narrative surrounding apparently English technical innovations has therefore often focussed on the recognition of English works in continental manuscripts, with these efforts most recently crystallised in Curtis and Wathey's 'Fifteenth-Century English Liturgical Music: A List of the Surviving Repertory'. The focus of discussion until now has generally been on a dichotomy between English and continental origin. However, as more details emerge of the opportunities for cultural cross-fertilisation, it becomes increasingly clear that this may be a false dichotomy. This thesis re-evaluates the complex issues of provenance and diffusion affecting the mid-fifteenth-century cyclic Mass. By breaking down the polarization between English and continental origins, it offers a new understanding of the provenance and subsequent use of many Mass cycles. Contact between England and the continent was frequent, multifarious and quite possibly reciprocal and, despite strong national trends, there exists a body of work that can best be understood in relation to international cultural exchange. This thesis helps to clarify the provenance of a number of Mass cycles, but also suggests that, for Masses such as the anonymous Thomas cesus and Du cuer je souspier, Le Rouge's So ys emprentid, and even perhaps Bedyngham's Sine nomine, cultural exchange is key to our understanding. This thesis also offers a more detailed overview of the chronology of fifteenth-century English Mass cycles and defines their various structural norms, as well as those Masses which depart from these.
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GOEDERT, THERESE. "Les organismes marins, sources de substances antitumorales". Strasbourg 1, 1994. http://www.theses.fr/1994STR15007.
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Nandy, Biplob Kumar. "Development and study of novel mid-infrared frequency conversion sources". Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670629.
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Tunable narrow-linewidth and broadband laser sources in the mid-infrared (mid-IR) wavelength range are extremely desirable in all time scales for their several useful applications in spectroscopy, imaging, optical communication and medical sciences to name a few. The one very important application of high-power tunable narrow-linewidth mid-IR laser sources in the 2 µm wavelength range is the ability to pump cascaded mid-IR optical parametric oscillators (OPO) for generating tunable wavelengths beyond 4 µm using semiconductor nonlinear crystals such as ZnGeP2 (ZGP) or orientation patterned GaAs (OP-GaAs). These crystals have very good linear and nonlinear optical properties along with good transparency beyond 4 µm wavelengths unlike oxide-based materials such as MgO:PPLN which have strong multi phonon absorption beyond 4 µm wavelengths. However, both ZGP and OP-GaAs cannot be pumped by commercially available 1 µm lasers due to linear and nonlinear absorptions below~2 µm wavelengths. In this thesis, we have demonstrated some very useful high-power narrow linewidth tunable 2 µm nanosecond and picosecond high-repetition-rate sources with very good spatial beam qualities. We have further demon strated a picosecond mid-IR idler-resonant MgO:PPLN based OPO with intra-cavity second-harmonic-generation (SHG). This helps in covering the essential wavelength gap between 1.064 µm and 1.45 µm when pumped by Yb- ber laser at 1.064 µm. This wavelength gap is generally not covered by MgO:PPLN based SROs that are signal resonant due to the material transparency of MgO:PPLN which doesn't allow the idler wave to go above ~4 µm wavelength, thereby restricting the signal wave from reaching below ~1.45 µm.Due to the requirement of synchronous pumping, the OPOs typically tend to be relatively bulky and of large size, which can restrict its practical utility in space-constrained applications. We address this challenge by demonstrating a compact picosecond high-repetition rate singly resonant (SRO) with intracavity-mirror-retro-re ector ber (IMRF) that enables two-fold reduction in the form-factor. This IMRF OPO demonstrates a high wavelength tunability from~1.45 µm to~4 µm with high spectral brightness and exceptionally good output beam quality. In our attempt to further reduce the size and complexity of nonlinear frequency conversion sources, we have demonstrated the rst single-pass optical parametric generation (OPG) and ampli cation (OPA) in MgO:PPLN with record high conversion e ciency of >59% without the requirement of any seed-laser. We have demonstrated a record-low pump threshold energy of 7.5 nJ which is remarkably small and opens a whole new area of research on single-pass frequency conversion devices based on OPG/OPA. Our system is highly tunable near~2 µm region with >8 W of single-pass output power while pumped with~14 W of pump power at 1064 nm. Finally, in this thesis, we have demonstrated the rst phase-locked picosecond OPO with record high output power and spectral bandwidth near~2 µm wavelength region. Such a device can be used as a high spectral brightness phase-locked super-continuum source for a huge array of applicationsLas fuentes láser de banda ancha y ancho de línea estrecho sintonizables en el rango de longitud de onda del infrarrojo medio (IR medio) son de gran interés en todas las escalas de tiempo por sus diversas aplicaciones en espectroscopia, imágenes, comunicación óptica y ciencias médicas, por nombrar algunas. Una aplicación muy importante de las fuentes láser de IR medio de ancho de línea estrecho sintonizable de alta potencia en el rango de longitud de onda de 2 μm es la capacidad de bombear osciladores ópticos paramétricos (OPO) de IR medio en cascada para generar longitudes de onda sintonizables más allá de 4 μm, usando cristales semiconductores no lineales tales como ZnGeP2 (ZGP) o GaAs con patrón de orientación (OPGaAs). Estos cristales tienen muy buenas propiedades ópticas lineales y no lineales junto con una buena transparencia más allá de las longitudes de onda de 4 μm, a diferencia de los materiales a base de óxido como MgO:PPLN que tienen una fuerte absorción de multifonones más allá de las longitudes de onda de 4 μm. Sin embargo, tanto ZGP como OP-GaAs no pueden ser bombeados por láseres de 1 μm disponibles comercialmente debido a absorciones lineales y no lineales por debajo de 2 μm de longitud de onda. En esta tesis, hemos demostrado algunas fuentes de alta potencia sintonizables de 2 μm de nanosegundos y picosegundos de alta tasa de repetición con muy buena calidad de haz espacial. Además, hemos demostrado un OPO basado en MgO:PPLN de picosegundos resonante para el campo idler en el IR medio, con generación de segundo armónico (SHG) intracavidad. Esto permite cubrir la brecha de longitud de onda esencial entre 1.064 μm y 1.45 μm cuando se bombea con láser de fibra de Yb a 1.064 μm. Esta brecha de longitud de onda generalmente no está cubierta por los SRO basados en MgO:PPLN, que resuenan el campo señal, debido a la transparencia del material de MgO:PPLN, que no permite que el campo idler supere las 4 μm de longitud de onda, lo que restringe el alcance del campo señal por debajo de 1.45 μm. Debido al requisito del bombeo síncrono, los OPOs suelen ser relativamente voluminosos y de gran tamaño, lo que puede restringir su utilidad práctica en aplicaciones con limitaciones de espacio. Abordamos este desafío demostrando un sistema de picosegundo compacto de alta tasa de repetición de resonancia simple (SRO) con un espejo retro reflector intracavidad en fibra (IMRF) que permite una reducción doble en el factor de forma. Este IMRF OPO demuestra una alta sintonización de longitud de onda de 1.45 μm a 4μm con un alto brillo espectral y una calidad de haz de salida excepcionalmente buena. En nuestro intento de reducir aún más el tamaño y la complejidad de las fuentes de conversión de frecuencia no lineal, hemos demostrado la primera generación óptica paramétrica (OPG) y amplificación (OPA) de un solo paso en MgO:PPLN con un récord de alta eficiencia de conversión de >59% sin necesidad de ningún láser de inicio. Hemos demostrado un umbral de energía de bombeo récord bajo de 7,5 nJ, que es notablemente pequeño y abre una nueva área de investigación sobre dispositivos de conversión de frecuencia de un solo paso basados en OPG/OPA. Nuestro sistema es altamente sintonizable cerca de la región de 2 μm con >8 W de potencia de salida de un solo paso mientras se bombea con 14 W de potencia de bombeo a 1064 nm. Finalmente, en esta tesis, hemos demostrado el primer OPO de picosegundos con ajuste de fases (mode-locked) con record en potencia de salida y un ancho de banda espectral cerca de la región de longitud de onda de 2 μm. Un dispositivo de este tipo se puede utilizar como una fuente supercontinua mode-locked de alto brillo espectral para una gran variedad de aplicaciones
12
Nicolas, José. "Caractérisation physico-chimique de l’aérosol troposphérique en Méditerranée : Sources et Devenir". Versailles-St Quentin en Yvelines, 2013. http://www.theses.fr/2013VERS0074.
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L’étude des impacts des aérosols troposphériques sur le climat régional et la qualité de l’air du bassin méditerranéen fait partie des enjeux de ChArMEx (The Chemistry-Aerosol Mediterranean EXperiment), dans lequel s’inscrit cette thèse. Ce travail repose sur un suivi annuel des propriétés physico-chimiques des aérosols sur le bassin occidental et sur deux campagnes intensives d’étude des propriétés de la matière organique particulaire sur les bassins Est et Ouest. Une nouvelle station de mesures atmosphériques, inaugurée en Corse (France, bassin Ouest) en juin 2012, permit d’établir un niveau régional des aérosols, inférieur au bassin Est. Une variabilité saisonnière des concentrations massiques des aérosols (diamètre : 1-10 µm) fut établie, liée aux poussières, aux aérosols secondaires et aux précipitations faibles en période estivale. L’autre fait nouveau est le degré d’oxydation très élevé -et peu variable- de la matière organique en été sur l’ensemble des deux bassinsThe study of tropospheric aerosols impacts on regional climate and air quality is amongst the objectives of ChArMEx (The Chemistry-Aerosol Mediterranean EXperiment), including the ones of this PhD. This work is based on annual observations of physico-chemical aerosol properties in the western basin, and on two intensive field campaigns dedicated on particulate organic matter in the two basins (Est and West). A new atmospheric station, started in Corsica (France, western basin) in June 2012, showed low background aerosol levels, lower than in the eastern basin. A seasonal variation of aerosol mass concentrations (diameter 1-10 µm) appeared, due to dust, secondary aerosols, and a deficit of rain in summer. An other striking point is the highly and constant oxidation state of organic aerosols in summer in the two basins
13
Ji, Lin. "Mid frequency vibration analysis of built up structures". Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289915.
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Sukeert, Sukeert. "Versatile nonlinear frequency conversion sources in the near- and mid-infrared". Doctoral thesis, Universitat Politècnica de Catalunya, 2022. http://hdl.handle.net/10803/674003.
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Tunable laser sources in different spectral regions are of interest for a variety of applications including spectroscopy, trace gas sensing, medical diagnostics, LIDAR and material processing. Existing lasers have limited tunability and many spectral regions continue to remain inaccessible to lasers due to lack of suitable gain media. Nonlinear frequency conversion is a viable approach to cover such difficult spectral regions in the visible, near and mid-infrared (mid-IR).
Optical parametric oscillators (OPO) can provide wide wavelength tunability with high output powers in good beam quality across continuous-wave (cw), nanosecond and ultrafast picosecond and femtosecond time-scales. With the development of quasi-phase-matched (QPM) nonlinear materials in fan-out grating structure, wide wavelength tuning is possible at a fixed temperature, enabling the development of rapidly tunable devices for practical applications. Difference-frequency-generation (DFG) is also an attractive approach for generating high powers in the mid-IR in a single-pass scheme.
In this thesis, we have developed second-order nonlinear frequency conversion sources based on nanosecond and cw OPOs and cw DFG. Widely tunable green-pumped OPOs have been developed by using fan-out grating structure for the first time in different nonlinear materials, and a high-power cw source in the mid-IR has been developed by exploiting DFG. The sources developed in this thesis cover a wavelength range spanning 677-2479 nm. One of the OPOs developed in this work has also been deployed in an industrial environment in a device characterization setup.
In green-pumped OPOs, we demonstrate a widely tunable cw OPO based on PPKTP in a fan-out grating structure. The OPO is continuously tunable across 742-922 nm in the signal, and 1258-1884 nm in the idler. Resonant wave output coupling has been deployed to extract useful signal power and reduce the thermal load, and the OPO can deliver up to 1.65 W of total output power. The use of output coupling results in superior performance of the OPO over pure singly-resonant oscillator (SRO) configuration.
We also develop the first green-pumped OPO based on MgO:cPPLT. Continuous wavelength tuning across 689-1025 nm in the signal and 1106-2336 nm in the idler at room temperature has been achieved in the nanosecond OPO by using a fan-out grating structure. The OPO can provide up to 131 mW of average output power at 25 kHz repetition rate, and the idler passive power stability is 3.9% rms over 30 minutes.
A cw OPO based on MgO:PPLN in a fan-out grating design is then described. The OPO is continuously tunable across 813-1032 nm in the signal and 1098-1539 nm in the idler. A short crystal length and signal output coupling are used to minimise thermal effects, and the OPO can generate up to 710 mW of total output power with signal and idler passive power stabilities better than 2.8% rms and 1.8% rms, respectively over 1 hour and signal M^2<1.1.
As a part of an industrial internship, a cw green-pumped MgO:PPLN OPO is developed at Radiantis. The OPO is used as the input light source of a device characterization setup to test sensors for the aerospace sector. Compared to the existing light source, using the OPO results in orders-of magnitude-higher response of the InGaAs sensor, leading to a more precise and accurate characterization, and lower measurement error, thus improving the device evaluation process.
Finally, we demonstrate a high-power cw source at 2.26 µm using the DFG process. The source can deliver up to 3.84 W of output power at 2262 nm, with a power stability better than 0.6% rms over 1 hour, in a Gaussian mode profile with M^2<1.2.Los láseres sintonizables en diferentes regiones espectrales presentan una amplia variedad de aplicaciones que incluyen espectroscopía, sensado de gases, LIDAR y procesamiento de materiales, entre otras. Los láseres existentes tienen una sintonizabilidad limitada y muchas porciones del espectro permanecen aún inaccesibles debido a la falta de medios activos con ganancia en dicha región. Un enfoque viable para cubrir las regiones espectrales en los rangos visible, infrarrojo cercano e infrarrojo medio (mid-IR) es mediante la conversión no lineal de frecuencias. Los osciladores paramétricos ópticos (OPO) proveen un amplio rango de sintonizabilidad con altas potencias y con calidad de haz excelente en escalas de tiempo de onda continua (cw), pulsado en nanosegundo y ultra rápido. Con el desarrollo de materiales no lineales que presentan la propiedad de quasi-phase-matching con estructura de red del tipo fan-out es posible sintonizar un amplio rango de longitudes de onda que habilitan el desarrollo de dispositivos sintonizables para aplicaciones prácticas en las que se requieran cambios de longitudes de onda de manera rápida. El proceso no lineal de generación de diferencia de frecuencias (DFG) es un enfoque atractivo para la generación de potencias altas en el mid-IR en esquemas de un solo paso a través del medio. En esta tesis se desarrollan fuentes de luz basadas en la conversión de frecuencias no lineal de segundo orden usando OPOs en los regímenes de cw y nanosegundos, y de cw que usan el proceso de DFG. Se desarrollan por primera vez OPO sintonizables bombeados por un láser verde usando estructuras de red fan-out en diferentes materiales. Además, se desarrolla una fuente de cw de alta potencia en el mid-IR usando DFG. Las fuentes desarrolladas en esta tesis cubren el intervalo de 677-2479 nm. Uno de los OPOs que se desarrollan en este trabajo se utilizó en una empresa como parte de un dispostivo de caracterización de sensores. En OPOs con láser de bombeo verde, se demuestra un OPO de cw sintonizable basado en un cristal PPKTP. La señal e idler generados por el OPO pueden sintonizarse en los intervalos 742-922 nm y 1258-1884 nm, respectivamente, y puede entregar una potencia máxima de 1.65 W. El uso del acoplamiento de salida da como resultado un rendimiento superior del OPO a la configuración de oscilador resonante individual pura. Se realiza la primera demostración de un OPO bombeado por láser verde basado en un cristal de MgO:cPPLT. Se consiguió a temperatura ambiente un intervalo para la señal de 689-1025 nm, y para el idler de 1106-2336 nm, en el OPO que opera en el régimen del nanosegundo. El OPO puede proveer hasta una potencia media de salida de 131 mW a una tasa de repetición de 25 kHz. Seguidamente se desarrolló un OPO de cw basado en un cristal de MgO:PPLN. La señal y el idler generados pueden sintonizarse en los rangos de 813-1032 nm y 1098-1539 nm, respectivamente. El OPO puede generar hasta 710 mW de potencia de salida total con una estabilidad pasiva de potencia de señal y de idler mejores que 2.8% rms y 1.8% rms, respectivamente, a lo largo de una hora, y con un valor M^2<1.1 para la señal. Luego se describe el desarrollo del OPO con bombeo verde de cw basado en un cristal de MgO:PPLN en el entorno industrial de la compañía Radiantis. El mismo se utiliza como la fuente de luz de entrada en un esquema de caracterización de dispositivos con el propósito de probar sensores para el sector aeroespacial. En comparación con la fuente de luz existente, el uso de OPO da como resultado una respuesta de órdenes de magnitud mayor que la de un sensor de InGaAs, mejorando de este modo el proceso de evaluación de los dispositivos. Finalmente, se demuestra una fuente de cw de alta potencia que opera en una longitud de onda de 2.26 µm usando DFG. La fuente puede entregar hasta 3.84 W de potencia de salida a 2262 nm, con una estabilidad de potencia mejor que 0.6% rms durante una hora, en un perfil de modo Gaussiano con M^2<1.2.
Fotònica
15
Petrova, Mariia. "Sources and processes governing mercury cycling in a changing Arctic Ocean". Electronic Thesis or Diss., Aix-Marseille, 2020. http://theses.univ-amu.fr.lama.univ-amu.fr/201119_PETROVA_347rbw227miou845bplinz648pejtfe_TH.pdf.
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Le mercure (Hg) dans l'Arctique est un important problème environnemental et de santé humaine. Il a été difficile de comprendre les concentrations élevées persistantes de méthylmercure (MeHg) dans le biote arctique et ses tendances. Plusieurs études de bilan de masse de Hg ont été menées pour mieux comprendre les sources, les puits et les processus régulant les tendances biologiques du Hg dans l'océan Arctique (OA). Ceci est un point critique, car la quantité de Hg résidant dans l’OA définit sa résilience aux changements externes, tels que l’augmentation des apports de Hg anthropique et le changement climatique. Dans ce travail, nous avons utilisé nos nouvelles observations, combinées aux dernières études de modélisation, pour établir un bilan affiné de mercure arctique et pour étudier l'importance relative des flux de mercure atmosphériques, océaniques et terrestres dans l’OA. Sur la base d'observations saisonnières complètes de Hg dissous et particulaire pour deux grands fleuves eurasiens, le Yenisei et le Severnaya Dvina, nous avons estimé le flux fluvial de Hg vers l'OA. En utilisant nos nouvelles données acquises lors de la campagne GEOTRACES TransArcII 2015 et de la campagne GEOTRACES GRIFF 2016 et en les combinant avec d'autres campagnes arctiques qui ont eu lieu en 2015, nous avons estimé les flux océaniques de Hg entre les océans Arctique et Atlantique, ainsi que l'exportation et l’enfouissement de Hg.Nous avons également étudié l'importance de la dérive transpolaire, connue pour transporter des matières et des éléments provenant des rivières eurasiennes à travers l’OAMercury (Hg) in the Arctic is an important environmental and human health issue. Understanding persistent high methylmercury (MeHg) concentrations in arctic biota and trends therein has been challenging. Several Hg mass balance studies were undertaken to gain insightinto the sources, sinks and processes regulating biological Hg trends in the Arctic Ocean (AO). This is a critical point, since the amount of Hg residing in the AO defines its resilience to external changes, such as altered inputs of anthropogenic Hg and climate change. In this work we used our new observations, combined with the latest modelling studies, to establish a refined Arctic Hg budget and to investigate the relative importance of atmospheric, oceanic, and terrestrial Hg fluxes in the AO. Based on comprehensive seasonal observations of dissolved and particulate Hg for two large Eurasian rivers, the Yenisei and the Severnaya Dvina, we estimated the Hg riverine flux to the AO. Using our new data acquired during the 2015 GEOTRACES TransArcII cruise and the 2016 GEOTRACES GRIFF cruise and combining them with other arctic cruises which took place in 2015, we estimated oceanic Hg fluxes between the Arctic and Atlantic Oceans, as well as the export and burial Hg fluxes. We also investigated the importance of the Transpolar Drift, known to carry Eurasian river sourced matter and elements across the AO
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Messineo, Giuseppe. "The MIR experiment: quantum vacuum and dynamical Casimir effect". Doctoral thesis, Università degli studi di Trieste, 2011. http://hdl.handle.net/10077/4572.
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2009/2010This thesis concerns one of the few low energy experimental efforts aiming to test Quantum Electrodynamics. The experiment MIR (Motion Induced Radiation) studies the quantum vacuum in the presence of accelerated boundaries. According to Quantum Electrodynamics, a non-uniformly accelerated mirror in vacuum feels a friction force due to the interaction with the vacuum photons. As a consequence, real photons are produced in the process, which is known as dynamical Casimir effect. The radiated energy is emitted at the expense of the mechanical energy of the mirror. The effect has never been observed experimentally, since it is very feeble. Only recently a few experimental approaches have been proposed. The theory of the dynamical Casimir effect has been treated extensively in literature. According to the models proposed, for harmonic oscillations the effect is proportional to the oscillation frequency. As all the papers refer to frequencies of the order of a gigahertz, it is not possible to tackle the problem of obtaining a moving boundary with a purely mechanical approach, for example employing piezoelectric transducers or acoustic excitations, due to the large amount of energy required to keep a massive object in motion. A solution to this problem was proposed at the end of the 80's and has been adopted in the MIR experiment. In this framework the moving boundary is a semiconductor slab that switches periodically from complete transparency to total reflection when illuminated by a train of laser pulses. In this way one obtains a time variable mirror which mimics a physical oscillation, without the burden of overcoming the inertia of the mirror. Even so, the number of photons expected is extremely small. The MIR experimental strategy to enhance the photon production is to have the mirror as the wall of a resonating cavity. In this case, if the repetition rate of the laser is about twice a resonance frequency of the cavity, a parametric amplification process occurs, resulting in an enhancement of the number of photons by a factor which depends on the Q-value of the cavity. To this end, superconducting cavities are employed in the experiment.
Questa tesi riguarda uno dei pochi esperimenti di bassa energia dedicati allo studio dell'Elettrodinamica Quantistica. L'esperimento MIR (Motion Induced Radiation) studia il vuoto quantistico in presenza di condizioni al contorno accelerate. Secondo l'Elettrodinamica Quantistica, uno specchio non uniformemente accelerato nel vuoto risente di una forza di attrito dovuta all'interazione con i fotoni del vuoto. In conseguenza di ciò in questo processo, noto come effetto Casimir dinamico, vi è produzione di fotoni reali. L'energia irradiata viene emessa a scapito dell'energia meccanica dello specchio. L'effetto è molto debole e non è mai stato osservato sperimentalmente. Solo di recente sono stati proposti alcuni approcci sperimentali, mentre gli aspetti teorici sono stati trattati ampiamente in letteratura. Secondo i modelli proposti, nel caso di oscillazioni armoniche l'effetto è proporzionale alla frequenza di oscillazione. Poiché tutti gli articoli fanno riferimento a frequenze dell'ordine di un gigahertz, con un approccio puramente meccanico, ad esempio impiegando trasduttori piezoelettrici o eccitazioni acustiche, non è possibile risolvere il problema di ottenere uno specchio in movimento a causa della grande quantità di energia richiesta per mantenere un oggetto massivo in moto. Una soluzione a questo problema è stata proposta alla fine degli anni '80 ed è stata adottata nell'esperimento MIR. L'idea è che la parete in movimento possa essere sostituita da un lastra di semiconduttore che periodicamente passa da uno stato di totale trasparenza ad uno di alta riflettività, per illuminazione da parte di un treno di impulsi laser. In tal modo è possibile ottenere un specchio variabile nel tempo che riproduce una oscillazione fisica, senza la necessità di superare l'inerzia dello specchio. Anche in questo caso tuttavia, il numero di fotoni previsto è estremamente ridotto. La strategia sperimentale di MIR per aumentare la produzione di fotoni è quella di utilizzare lo specchio variabile come parete di una cavità risonante. Se la frequenza di ripetizione del laser è circa due volte la frequenza di risonanza della cavità, si verifica un processo di amplificazione parametrica, con un conseguente aumento del numero di fotoni prodotti. Poiché questo incremento dipende dal Q-valore della cavità, nell'esperimento vengono impiegate cavità superconduttrici.
XXIII Ciclo
1980
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Rodrigues, Alcide Conceicao Do Rosario. "A high performance transistorised power source for MIG welding". Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/34817.
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This research concerns an investigation into the application of Power Electronics to high performance power sources for precise and efficient control of the pulsed-current metal-inert gas (PCM) welding processes. The physical processes of the welding arc are reviewed and the characteristics of a number of power sources are considered prior to preparing the operational specification for the PCM power source. From a number of possibilities the high frequency switching regulator operating in the secondary side of the power transformer was selected for detailed study. The power source was based on the use of state-of-the-art power transistors operating in a switching mode to minimise losses and to give a fast response for good welding performance. The basic operating frequency was chosen to be at the very limit of the audio range. The dynamic behaviour of the transistors and associated protection networks is critical and failure to meet all the operating limits of the transistor can be costly. To assist with the thorough understanding of the circuit behaviour and to predict the transistor switching waveforms a digital computer model was developed. This gave good correlation with experimental results observed with the completed power source. Tests were carried out with the welding power source and showed that there was no discernable difference in the weld quality when compared with those produced by the more expensive series linear regulator power source. As a direct result of the study a new range of power sources meeting exacting standards have been made available to the welding industry.
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Roy, Anthony. "Gestion optimale d'un système multi-sources pour un site isolé en mer". Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4067.
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La production d’énergie électrique dans les zones isolées en mer doit faire face à de nombreuses contraintes technico-économiques, liées à la satisfaction de la demande et à l’importation coûteuse du combustible nécessaire aux moyens de production à partir d’énergies fossiles. Avec le récent développement des sources d’énergie marine renouvelable, de nouvelles perspectives apparaissent pour l’alimentation des sites isolés en mer, dans une optique de dé-carbonisation de la production d’énergie. Ainsi, il est proposé dans ces travaux de thèse d’étudier le dimensionnement et la gestion d’un micro-réseau insulaire composé de panneaux solaires photovoltaïques, d’éoliennes, d’hydroliennes, de houlogénérateurs et de batteries.Une analyse préalable des ressources exploitées permet de mettre en avant quelques complémentarités et non-complémentarités. Afin de minimiser l’insatisfaction de la demande et le coût de l’énergie produite, une optimisation combinée du dimensionnement et de la gestion de l’énergie est proposée. Différentes stratégies de gestion de la demande sont appliquées de manière hiérarchique sur plusieurs charges, pour éviter l’apparition de situations critiques. Les résultats obtenus montrent que l’application d’une gestion de la demande permet de réduire le coût de production de l’électricité en diminuant la quantité de stockage nécessaire. Par ailleurs, la diversification des sources utilisées offre de nombreux avantages. Enfin, la capacité des algorithmes développés à gérer correctement un micro-réseau en temps réel est validée sur un banc expérimentalThe electrical power generation in remote maritime areas must face many technical-economicconstraints related to the load satisfaction and the expensivefuel import for fossil based sources. Thanks to the recent development of marine renewable energies, new perspectives appearfor the electrical power supply of maritime remote areas, so asto decarbonize the electrical power generation. In this thesis, it is proposed to study the sizing and the energy management of anislanded microgrid madeof solar photovoltaic panels, wind turbines, tidal turbines, wave energy converters and batteries. A preliminary analysis of the harnessed resources allows some complementarities and non-complementaritiesto be highlighted. In order to reduce the unmet load demand and the cost of energy, a combined sizing and energy management optimization isproposed. Several demand-side management strategies are hierarchically applied on several loads, in order to avoid the occurrence of critical situations. The obtained results show that demand-side management allows the cost of energy to be reduced by decreasingthe amount of required storage. Also, thediversification of the sources brings many benefits. Finally, the ability of the developed algorithms tocorrectly manage the micro-grid in real time is validated on an experimental test bench
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Schoun, Stephen Bradley. "Attosecond High-Harmonic Spectroscopy of Atoms and Molecules Using Mid-Infrared Sources". The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1436853089.
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Hasselbalch, James Matthew. "Sources of job satisfaction and dissatisfaction among mid-grade Coast Guard officers". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA238056.
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Thesis (M.S. in Management)--Naval Postgraduate School, June 1990.Thesis Advisor(s): McGonigal, Richard A. ; Thomas, Kenneth W. "June 1990." Description based on title screen as viewed on March 23. 2010. Author(s) subject terms: Job Satisfaction, Intrinsic Motivation. Includes bibliographical references (p. 63). Also available in print.
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Hoareau-Osman, Magali. "Caractérisation fonctionnelle des ARN nucléolaires U8 et U13 et des microARN du cluster miR-379/410". Toulouse 3, 2010. http://www.theses.fr/2010TOU30333.
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Ces dernières années, le monde du non-codant a connu une formidable expansion grâce à la découverte de nouveaux petits ARNnc régulateurs chez les mammifères. Certains d'entre eux présentent des caractéristiques encore jamais observées puisqu'ils peuvent être tissu-spécifiques, répétés en tandem ou soumis à l'empreinte génomique parentale. Cependant, la fonction de beaucoup d'entre eux reste à ce jour inconnue. Nos travaux ont porté, par des approches de perte de fonction, sur la caractérisation fonctionnelle d'ARN appartenant à deux grandes familles de petits ARNnc : les ARN nucléolaires à boîtes C/D (snoARN C/D) et les microARN. Les snoARN C/D sont connus pour participer à la biogenèse des ARN ribosomiques (ARNr) et du petit ARN du spliceosome U6 (snARN U6). Afin d'étudier la fonction de deux snoRNP humaines, U8 et U13, nous avons développé une nouvelle technique d'inactivation de ces ARN C/D dans des cellules en culture, basées sur l'utilisation d'oligonucléotides antisens modifiés appelés LNA (Locked Nucleic Acids). Nous avons ainsi pu démontrer, pour la première fois, l'importance de snoRNP humaines pour la croissance cellulaire ainsi que leur rôle éventuel de chaperon dans des conditions de stress cellulaire. De plus, nous avons montré pour U8 une implication dans la biogenèse des ARN ribosomiques. Ces travaux constituent donc une première étape dans l'étude systématique des nombreux snoARN de mammifères dont la fonction est encore inconnue. Les microARN sont des régulateurs de l'expression des gènes à un niveau post-transcriptionnel. Nos travaux portent sur le cluster de microARN murin miR-379/410, codant pour 54 microARN et représentant près de 10% des microARN murins identifiés à ce jour. Il est situé au locus Dlk1-Dio3, une région ayant la particularité d'être soumise à l'empreinte génomique parentale, un mécanisme épigénétique qui conduit à une expression monoallélique des gènes, et ce de manière strictement dépendante de l'origine parentale du chromosome qui porte les allèles. Afin d'étudier la fonction des microARN du cluster miR-379/410, nous avons généré une lignée de souris knockout pour ce cluster. Nos premiers résultats montrent que ces microARN sont importants pour la viabilité post-natale des souris ainsi que pour leur croissance. Ces travaux constituent une avancée importante dans la compréhension du rôle des miARN chez les mammifèresIn the past few years, non-coding world has greatly expanded thanks to the discovery of new small regulatory ncRNAs in mammals. Some of them have particular features, as they may be tissue-specific, repeated in tandem or subjected to genomic imprinting. However, the function of many of them remains unknown. Our work has focused, using loss of function approaches, on the functional characterization of RNAs from two large families of small ncRNAs: C/D box small nucleolar RNAs (snoRNAs) and microRNAs. C/D snoRNAs are known to participate in the biogenesis of ribosomal RNAs (rRNAs) and small spliceosome U6 RNA (U6 snRNA). To investigate the function of two human snoRNPs, U8 and U13, we developed a new inactivation technique of C/D RNAs in cultured cells, using modified antisense oligonucleotides called LNA (Locked Nucleic Acids). We were able to demonstrate, for the first time, the importance of human snoRNPs for the cell growth and their possible role as a chaperone under conditions of cellular stress. Furthermore, we showed the involvement of U8 in the biogenesis of ribosomal RNAs. Thus, this work is a first step in the systematic study of many mammalian snoRNAs whose function is still unknown. MicroRNAs are regulators of gene expression at a posttranscriptional level. Our work focused on the cluster of murine microRNAs miR-379/410, encoding 54 miRNAs that represent nearly 10% of murine miRNAs identified to date. It is located in the DLK1-DIO3 locus, a region subjected to genomic imprinting, an epigenetic mechanism that leads to monoallelic expression of genes dependent on the parental origin of chromosome that carries the alleles. To study the function of microRNAs cluster miR-379/410, we generated a knockout mouse line for that cluster. Our first results show that these miRNAs are important for mice postnatal viability as well as for their growth. This work represents an important advance in understanding miRNAs roles in mammals
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Gonçalves, Tristan. "Implication du collagène XXV dans la myogenèse chez la souris Collagen XXV regulates myogenic differentiation and muscle formation Non-coding RNAs in skeletal muscle regeneration". Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCB117.
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La matrice extracellulaire (MEC) est impliquée dans les mécanismes de prolifération, migration, différenciation et d’adhésion cellulaire. La membrane basale (MB), MEC entourant le muscle, sert de soutien aux fibres musculaires durant la contraction donnant ainsi une élasticité aux fibres musculaires. La MB est composée de collagènes dont majoritairement le collagène IV, de laminines, de nidogène (entactine), de perlecan (heparan sulphate proteoglycan), et de protéoglycans. Au cours de la myogenèse, la modulation de la MEC est indispensable au bon déroulement des processus de délamination, migration et fusion des cellules musculaires. Le collagène XXV est un collagène de la famille MACIT (Membrane Associated Collagens with Interrupted Triple Helices). Cette famille de collagènes transmembranaires contient 3 autres membres : le collagène XIII, le collagène XVII et le collagène XXIII. Le collagène XIII est impliqué dans les processus de migration cellulaire, le collagène XXIII dans ceux d’adhésion cellulaire. Le collagène XXV est impliqué dans la maladie d’Alzheimer, par sa fixation aux agrégats de peptides Aβ. D’autre part, il a été montré qu’il est nécessaire à la mise en place de la jonction neuromusculaire dans le muscle du diaphragme. La souris col25a1-/- présente une aplasie et une atrophie du diaphragme à E18.5 probablement dues au défaut d’innervation. L’expression du collagène est précoce dans la myogenèse, puisqu’il est fortement exprimé dans le bourgeon de membre d’embryons de souris dès E12.5, bien avant l’innervation des muscles des membres. Le rôle du collagène XXV dans la myogenèse précoce n’est pas connu. Le but de mon travail est de démontrer le rôle du collagène XXV durant la myogenèse. Pour ce faire, des études in vivo et in vitro ont été menées. In vitro, nous montrons l’implication du collagène XXV dans la différenciation myogénique. In vivo, la souris col25a1-/- présente des défauts de formation de fibres plurinucléées dans les bourgeons de membre d'embryons prélevés à E12.5 et E14.5, ce qui démontre le rôle de ce collagène dans les processus de fusion des myoblastes en myotubes au cours de la myogenèse primaire. Nous démontrons aussi la régulation de l’ARNm de ce collagène par deux microARN : miR-208b et miR-499, sans effet additionnel ou synergique de ces deux miRs. Nos résultats complémentaires suggèrent que l'expression de col25a1 est probablement régulée par le facteur de transcription NFATc2. En effet, chez les embryons de souris nfatc2-/- prélevés à E12.5, nous observons une diminution de l’expression de col25a1, ce qui pourrait expliquer l’atrophie musculaire observée chez la souris nfatc2-/-. Il serait intéressant de restaurer ce défaut musculaire chez la souris nfatc2-/- en surexprimant ce collagène XXV chez cette sourisExtracellular matrix is involved in cellular proliferation, migration, differentiation and adhesion. Muscle extracellular matrix, called the basement membrane, serves as support for muscle fibers during contraction, thus giving elasticity to the muscle fibers. Basement membrane is composed by collagen mainly collagen IV, laminin, nidogen, perlecan (heparan sulphate proteoglycan) and proteoglycan. During myogenesis, the modulation of extracellular matrix is very important for muscle cells to delaminate, migrate and fuse. Collagen XXV is part of the MACIT (Membrane Associated Collagens with Interrupted Triple Helices) collagen family together with collagen XIII, collagen XVII and collagen XXIII. Collagen XIII is involved in cell migration and collagen XXIII in cell adhesion. Collagen XXV was first described in Alzheimer disease, as a component of the Aβ amyloid aggregates. Furthermore, Collagen XXV is necessary for the formation of neuromuscular junctions in diaphragm. At E18.5, col25a1-/- embryos show muscle aplasia and atrophy in diaphragm, probably due to lack of innervation. This collagen is strongly expressed during primary myogenesis in limb buds from E12.5 embryos, long before innervation of limb muscles. But the role of this collagen during early myogenesis has never been analyzed. In this work, I demonstrated the role of collagen XXV during early myogenesis. In vitro assays showed that collagen XXV is involved in the muscle differentiation process. In vivo, limb muscles from E12.5 and E14.5 col25a1-/- embryos have defects in the formation of plurinucleated myofibers, suggesting a role of this collagen in the fusion of myoblasts into myotubes during mouse myogenesis. In this work, I demonstrated that col25a1 transcripts are down-regulated by miR-208b and miR-499 without synergic or additional effects. Complementary results suggest that col25a1 expression could be regulated by the transcription factor, NFATc2. In E12.5 nfatc2-/- embryos, col25a1 expression is decreased. This result could explain the muscle atrophy observed in nfatc2-/- mice. It could be interesting to restore muscle atrophy in nfatc2-/- mouse by overexpressing col25a1 in these mice
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Randall, Kevin. "La glace de mer arctique : Source ou puits d'oxyde nitreux?" Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27428/27428.pdf.
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L’oxyde nitreux (N2O) est un gaz à effet de serre dont la présence dans la stratosphère contribue aussi à la destruction de l’ozone. Le but de cette étude, était de déterminer la présence de N2O dans la glace de mer de l’océan Arctique et d’évaluer l’impact de cette source potentielle sur l’atmosphère. Les concentrations totales de N2O dans les derniers 10 cm de la glace de mer et dans l’eau de surface sous-jacente au couvert de glace ont été quantifiées dans la mer de Beaufort de mars à avril 2008. Nos mesures ont mis en évidence des concentrations totales en N2O faibles et constamment sous-saturées par rapport à l’eau de surface sous-jacente au couvert de glace (ca. 40%) et à l’atmosphère (ca. 30%). Nous expliquons cette sous saturation par un rejet de la saumure riche en N2O lors de la formation de la glace à l’automne et à l’hiver. La glace de mer pourrait donc représenter une source de N2O pour l’atmosphère arctique pendant ces périodes.Nitrous oxide (N2O) is a greenhouse gas which also plays a role in stratospheric ozone depletion. The objective of this study was to demonstrate the presence of N2O in Arctic sea ice, and to quantify the impact of this potential source to the atmosphere. Bulk concentrations of N2O in the bottom 10 cm of the sea ice and in the underlying surface waters were measured in the Beaufort Sea from March to April 2008. Our sea ice measurements revealed low N2O bulk concentrations with N2O being consistently undersaturated with respect to the underlying surface water (ca. 40% saturation) and the atmosphere (ca. 30% saturation). The most plausible mechanism to explain the low N2O sea ice concentrations is a loss of N2O via brine rejection during sea ice formation in autumn and winter. Sea ice could thus act as a source of N2O via brine rejection during sea ice formation in autumn and winter.
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Krogen, Peter Ra. "A novel few-cycle optical source in the mid-infrared". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93067.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 43-45).
In this thesis, I designed, simulated, and implemented a novel optical pulse generation system which is shown to be able to generate exceptionally short optical pulses in the mid-infrared, tunable from 2-4[mu]m with pulse widths as low as 1.5 optical cycles at 3.5[mu]m (18fs). Energies as high a 1[mu]J were achieved, representing a peak power of roughly 100MW, at a 1kHz repetition rate, with excellent beam quality. The system was based on adiabatic difference frequency generation in an aperiodically polled lithium niobate crystal of an amplified, mode-locked Ti:Sapphire laser system.
by Peter Ra Krogen.
S.M.
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Krogen, Peter Ra. "A novel single-cycle optical source in the mid-infrared". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105945.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 90-106).
In this thesis, I demonstrate the generation of single-optical-cycle pulses in the mid-infrared, which are generated using adiabatic difference frequency in an aperiodically polled lithium niobate crystal. The input pulses were generated in amplified Ti:Sapphire laser system, the construction of which is covered in detail, along with complete characterization of the generated pulses. The generated pulses have a bandwidth spanning (1.8-4.5[mu]m), energy in excess of 1[mu]J at a 1kHz repetition rate, and are compressed to within 15% of their Fourier transform limited duration of 10fs, which is 1.1 optical cycles at their central wavelength of 2.6[mu]m, and represents a peak power well in excess of 100MW. Furthermore, intrinsic to the design of the system is the ability to shape both the spectral amplitude and phase of the generated pulses, which makes this source immediately suitable for applications requiring shaped pulses.
by Peter Ra Krogen.
Ph. D.
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D'AMBROSIO, DAVIDE. "Characterizing a Mid-IR laser source with a molecular beam". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2749554.
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Seiter, Michael. "Novel pulsed difference-frequency laser sources for compact mid-infrared trace-gas sensors /". Zürich, 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13354.
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Scantamburlo, Elisabetta <1976>. "Zen and Zenga as sources of influence in mid-twentieth century Western art". Doctoral thesis, Università Ca' Foscari Venezia, 2005. http://hdl.handle.net/10579/144.
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TOLIOPOULOS, DIMOSTHENIS. "Single photon sources integrated on Ge Mie resonator fabricated by solid state dewetting". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2021. http://hdl.handle.net/10281/311361.
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-The following Ph.D. thesis summarizes the work that has been made aiming at the fabrication and characterization of quantum emitters integrated inside Ge nanoisland on Si substrates. We choose to induce localized Ge impurities centers inside a thin layer of Al0.25Ga0.75As epitaxially grown on Ge islands acting as dielectric Mie Resonators (MR’s). These centers are working as light sources, capable of single photon emission and quantum entanglement properties. Fabrication of the Ge islands was done by solid state dewetting in an ultra-high vacuum environment, obtaining both amorphous and monocrystalline islands, with sizes ranging from 50 to 500 nm. These islands are also photonic Mie-resonators enhancing light-matter interaction and steering the localized defects emission, acting as dielectric nanoantennas. This thesis exploits molecular beam epitaxy, solid state dewetting and electron assisted lithography for realizing patterned samples. Many different characterization methods have been used to assess the quality of the fabricated samples. We use morphological characterization via scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optically, we characterized the Mie resonators by dark field (DF) spectroscopy to ensure their photonic mode appearance. Also, the crystallinity of the Ge seeds was investigated by RAMAN spectroscopy. In the end, the optical response of the samples will be tested by micro and macro Photoluminescence, time-resolved measurements, and auto-correlation measurements to assess the quantum nature of the emission at low temperatures. Towards our goal we faced three main different topics: i) the growth of Ge nanoisland via solid state dewetting, ii) the optimization of the photonic response of semiconductor Mie resonators by engineering the geometry of the substrates, iii) the integration of III-V layers on Ge islands and the observation of interesting associated defects. Each of these aspects is described in detail in chapters 3,4 and 5. During my secondments at UNIFI, I had also been involved in a quite different approach towards the deterministic realization of quantum emitters integrated beneath a glass nanoantenna, an activity which led to article submission, but it is not reported in this thesis.
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Duriez, Alban. "Origine et processus de minéralisation d'eaux thermales en milieu continental méditerranéen : Cas du système géothermal des thermopyles (Grèce)". Paris 11, 2006. http://www.theses.fr/2006PA112356.
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Robson, Thomas A. "A burning need to know the use of open source intelligence In the fire service /". Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Mar/09Mar%5FRobson.pdf.
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Thesis (M.A. in Security Studies (Homeland Security and Defense))--Naval Postgraduate School, March 2009.Thesis Advisor(s): Bergin, Richard ; Simeral, Robert. "March 2009." Description based on title screen as viewed on April 24, 2009. Author(s) subject terms: Fire, Intelligence, Firefighter Training, First Responders, Fire Service Intelligence, Open Source Intelligence, Fire Service. Includes bibliographical references (p. 77-79). Also available in print.
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Laghdass, Mélissa. "Réponse de la communauté bactérienne marine à différentes sources nutritives : lien entre activité et diversité". Paris 6, 2010. http://www.theses.fr/2010PA066463.
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L’étude de la relation entre la structure des communautés bactériennes marines et des différentes sources nutritives est essentielle à une meilleure compréhension du rôle des groupes bactériens dans les cycles biogéochimiques des éléments. Dans le cadre de cette thèse, des approches in situ et expérimentales couplées aux différentes techniques de biologie moléculaires ont été utilisées pour étudier cette question. L’impact des poussières Sahariennes sur la structure de la communauté bactérienne a été abordé par le déploiement des mésocosmes sur un site oligotrophe côtier de la Corse. Malgré la forte évolution temporelle de la structure de la communauté bactérienne au cours de l’expérience, une réponse à l’ajout de poussières a été détectée au rang taxinomique du genre illustrée par une augmentation de l’activité d’Alteromonas macleodii. Une étude menée sur un site hauturier oligotrophe en Mer Méditerranée Nord Occidentale a mis en évidence que la matière organique associée aux masses d’eau dessalée stimulait la production bactérienne hétérotrophe. Par contre, ces masses d’eau dessalée n’était pas associées à une diversité bactérienne particulière. La forte production observée était attribuable à peu d’OTUs cosmopolites. L’activité du cluster SAR11 dans différents conditions de limitations en nutriments a été étudiée. Un suivi de l’abondance et de l’activité de SAR11 sur une année a permis de montrer que SAR11 est un composant actif de la communauté bactérienne et que son activité est représentative de celle de la communauté bactérienne globale à la station MOLA. De plus l’activité de SAR11 était positivement liée à la limitation en P.
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Nicolaou, Elie. "Le mont Athos et la mer Egée : les propriétés du monastère de Xeropotamou à Naxos". Paris 4, 1988. http://www.theses.fr/1988PA040008.
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Ce travail est divisé en deux parties. La première comporte : l'introduction (renseignements sur le mont Athos et Naxos; géographie, histoire, population). Le premier chapitre se réfère aux relations religieuses entre le mont Athos et Naxos. Le deuxième chapitre est relatif à la principale propriété de Xeropotamou, le métoque des quarante martyrs. Le troisième concerne le contenu judiciaire de notre dossier et le dernier est une approche linguistique. La deuxième partie consacrée à l’édition de nos quarante documents post-byzantins, comprend les règles suivies et la table des documents. Pour chaque document, on trouve le titre, la date, son résumé, sa description; le texte est présenté selon la méthode littéraire. A la fin du texte on trouve l'explication des mots étrangers, ainsi que les notes. Une bibliographie sélective, des appendices (listes, cartes, photos) et la table des matières complètent notre thèseThis thesis is divided in two parts : the first part consists of the introduction (information on mount Athos and Naxos; geography, history, population). The first chapter is on religious relations between mount Athos and Naxos. The second chapter refers to the main estate of Xeropotamou, the metoque of the forty martyrs. The third chapter concerns the judicial part of our work and the last is a linguistic approach. The second part is consecrated to the edition of our forty post-byzantine documents and shows the rules which have been followed, gives the contents of the documents. For each document, one finds the title, the date, a summary, a description; the presentation of the text is according to the literary method. Explanation of the foreign words, as well as notes are at the end of the text. A selective bibliography, appendices complete our thesis
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Le, Guillou Sandrine. "Du miRNome au rôle de miR-30b : implication des microARN dans la glande mammaire". Versailles-St Quentin en Yvelines, 2013. http://www.theses.fr/2013VERS0024.
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La glande mammaire est un organe dynamique, passant par des stades de prolifération, de différenciation puis de dédifférenciation au cours de cycles de reproduction. La compréhension des mécanismes régulant ces différentes étapes est un enjeu de recherche important. Parmi les régulateurs potentiels, l’implication de nouveaux acteurs, les microARN, a été récemment démontrée. Aujourd’hui, les données relatives à l’identification des microARN et de leur rôle dans la glande mammaire normale sont encore rares et concernent surtout l’étude de leur expression anormale lors de cancers du sein. Au cours de ce travail de thèse, une approche globale a été développée afin de décrire, pour la première fois, l’ensemble des microARN exprimés, le miRNome, dans la glande mammaire murine et bovine en lactation. Leur analyse a mis en évidence de nouveaux microARN potentiels et une signature de la glande mammaire, définie par 15 microARN, dont deux potentiellement spécifiques de la lactation. Les microARN actifs, présents dans RISC, ont été analysés afin de préciser le miRNome « fonctionnel » de la glande mammaire pendant la lactation. Par ailleurs, le rôle du microARN miR-30b dans le développement et la différenciation des cellules épithéliales mammaires a été défini à l’aide de souris transgéniques sur-exprimant ce microARN, montrant que la dérégulation d’un seul microARN peut provoquer un fort dysfonctionnement mammaire. La combinaison de ces deux approches a apporté des éléments nouveaux permettant la compréhension de l’impact des microARN sur la régulation du développement normal de la glande mammaireThe mammary gland is a dynamic organ, undergoing proliferation, differentiation and dedifferentiation stages during reproductive cycles. Understanding the mechanisms regulating these stages is a major research challenge. Among others potential regulators, the involvement of new molecules, the microRNA, has recently been demonstrated. Until now, data relating to the identification of microRNA and their role in mammary gland are still scarce and mainly concern the study of their abnormal expression in breast cancer. In this PhD work, a global approach has been developed to describe, for the first time, all expressed microRNA, the miRNome, in murine and bovine lactating mammary gland. This analysis revealed new potential microRNA and defined a mammary gland signature of 15 microRNA, including two that seems lactation stage-specific. Active microRNA, present in RISC, have been analyzed to specify the “functional” miRNome in lactating mammary gland. Moreover, the role of the microRNA miR-30b in the development and differentiation of mammary epithelial cells has been defined using transgenic mice over-expressing this microRNA, showing that the deregulation of a single microRNA can cause a large mammary dysfunction. The combination of these two approaches has provided new evidence for understanding the impact of microRNA on the regulation of the normal development of the mammary gland
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Ayou, Dereje Sendeku. "Combined absorption power and refrigeration systems driven by low and mid-grade heat sources". Doctoral thesis, Universitat Rovira i Virgili, 2014. http://hdl.handle.net/10803/306436.
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Hi ha una gran abundància de fonts de calor de baixa i mitja temperatura (<300 ° C), com pot ser la solar tèrmica, geotèrmica o calor residual de diversos processos tèrmics. Els principals serveis energètics com l'aire condicionat, la refrigeració o l'electricitat es generen en general per separat mitjançant diverses tecnologies de conversió d'energia independents. La majoria dels usuaris finals necessiten almenys més d'un servei energètic: un exemple típic d'això ho constitueix el servei energètic a edificis. La producció combinada d'electricitat (descentralitzada) i de fred mitjançant sistemes eficients de conversió d'energia accionats tèrmicament és una de la solució tecnològica adequada per fer front als actuals reptes relacionats amb l'energia a nivell mundial.
L'objectiu d'aquesta tesi és el desenvolupament d'una nova classe de cicles d'absorció per a la producció d'energia mecànica o elèctrica i refrigeració mitjançant fonts d'energia de baixa i mitjana temperatura. Per aconseguir aquest objectiu, es presenta primer una revisió dels cicles d'absorció combinats proposats a la literatura. Es presenten i discuteixen més els criteris d'acompliment utilitzats en la literatura. A continuació, es proposen diversos nous cicles d'absorció combinats. Aquests són analitzats i discutits des del punt de vista energètic i exergètic per a la utilització eficaç de les fonts de calor de baixa i mitjana temperatura. Com fluids de treball s’han utilitzat mescles a base d'amoníac: NH3 / H2O, NH3 / LiNO3 i NH3 / NaSCN. S'ha desenvolupat un model semi-empíric per a un expansor de desplaçament utilitzant amoníac (i barreja d’amoníac / aigua amb alta concentració d'amoníac) com a fluid de treball. Aquest model s'ha integrat en alguns dels cicles d'absorció combinats proposats en aquesta tesi. Posteriorment, s'ha realitzat un model de sistema d'absorció per a la producció de potència i refrigeració solar (SAPCS) per usar-lo en l'eina de simulació dinàmica TRNSYS com un cas representatiu per a la integració dels cicles d'absorció combinats amb una planta termosolar.Existe una gran abundancia de fuentes de calor de baja y media temperatura (<300 ° C), como puede ser la solar térmica, geotérmica o calor residual de diversos procesos térmicos. Los principales servicios energéticos como el aire acondicionado, la refrigeración o la electricidad se generan por lo general por separado mediante diversas tecnologías de conversión de energía independientes. La mayoría de los usuarios finales necesitan por lo menos más de un servicio energético: un ejemplo típico de esto lo constituye el servicio energético a edificios. La producción combinada de electricidad (descentralizada) y de frío mediante sistemas eficientes de conversión de energía accionados térmicamente es una de la solución tecnológica adecuada para hacer frente a los actuales desafíos relacionados con la energía a nivel mundial. El objetivo de esta tesis es el desarrollo de una nueva clase de los ciclos de absorción para la producción de energía mecánica o eléctrica y refrigeración mediante fuentes de energía de baja y media temperatura. Para lograr este objetivo, se presenta primero una revisión de los ciclos de absorción combinados propuestos en la literatura. A continuación, se proponen varios nuevos ciclos de absorción combinados. Estos son analizados y discutidos desde el punto de vista energético y exergético para la utilización eficaz de las fuentes de calor de baja y media temperatura. Como fluidos de trabajo se utilizaron mezclas a base de fluidos de trabajo de amoníaco: NH3 / H2O, NH3 / LiNO3 y NH3 / NaSCN. Se ha desarrollado un modelo semi-empírico para un expansor de desplazamiento usando amoniaco (y mezcla de amoniaco / agua con alta concentración de amoniaco) como fluido de trabajo. Este modelo se ha integrado en algunos de los ciclos de absorción combinados propuestos en esta tesis. Posteriormente, se ha realizado un modelo de sistema de absorción para la producción de potencia y refrigeración solar (SAPCS) para usarlo en la herramienta de simulación dinámica TRNSYS como un caso representativo para la integración de los ciclos de absorción combinados con una planta termosolar. En conclusión esta tesis contribuirá al desarrollo de una nueva clase de sistemas de absorción capaces de proporcionar energía y refrigeración de forma simultánea y/o alternativamente, mediante la utilización de fuentes de calor
Low and mid-grade heat sources (< 300 °C), such as solar thermal, geothermal and waste heat from various thermal processes are abundantly available. Air-conditioning, refrigeration and electricity are useful forms of energy products, usually produced using separate energy conversion technologies. Most end-users need at least dual energy products: typical example could be buildings applications. The combined production of electricity (decentralized) and cold using efficient thermally-driven energy conversion systems are one of the suitable technological solution to address the current global energy related challenges. The aim of this thesis is the development of a new class of absorption cycles to produce mechanical or electrical energy and cooling using energy sources at low or medium temperature. To achieve this aim, first combined absorption cycles proposed in the literature are reviewed. The concept of combined absorption cycles are explained in terms of idealized energy conversion systems. Performance criteria used in the literature are presented and discussed. Then, several new combined absorption cycles are proposed, analysed and discussed from the energetic and exergetic viewpoints for the effective utilization of low and mid-grade heat sources. Ammonia based working fluid mixtures were used: NH3/H2O, NH3/LiNO3 and NH3/NaSCN. A semi-empirical model for a scroll expander using ammonia (and ammonia/water mixture with high concentration of ammonia) as working fluid is developed. It is integrated into some of the proposed combined absorption cycles in this Thesis. Then, a Solar Absorption Power and Cooling System (SAPCS) model is developed for its use in TRNSYS software as a simulation tool and it is used to demonstrate a representative case for the integration of combined absorption cycles with solar thermal plant. In conclusion this thesis will contribute to the development of new class of absorption systems able to provide power and refrigeration simultaneously and/or alternatively by utilizing low and mid-grade heat sources.
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Al-kadry, Alaa. "Mid-infrared soliton self-frequency shift and supercontinuum sources based on As2Se3 chalcogenide microwires". Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=123226.
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In this thesis, I propose tunable mid-Infrared (IR) sources based on the soliton self frequencyshift (SSFS) and supercontinuum (SC) generation in As2Se3 microwires. First, Ipresent two methods to maximize the SSFS in microwires with diameter profiles varyingnon-uniformly along the soliton propagation path. There are two steps in each method.The first step consists in selecting the input microwire diameter that leads to the highestrate of soliton frequency shift per unit length. The second step consists of graduallyincreasing the microwire diameter along the soliton path such that a wavelength-shiftingsoliton experiences only weak perturbations from the third-order dispersion and avoidsshedding its energy into non-solitonic radiation. The optimized profile supports solitonswith different input energies that allow the tuning of a self-frequency shifted solitonover a spectral range of 860 nm in the mid-IR wavelength regime using only a 10 cmmicrowire length. The results are compared with the SSFS generated in microwires withuniform diameter profile to illustrate the enhancement of wavelength shift in the designednon-uniform microwire. This is the first study of the SSFS in As2Se3 microwires.Second, I present the limitations of the two-photon absorption (TPA) effect on generatinga mid-IR SC using femtosecond pump soliton sources operating at 1550 nmwavelength. A solution to avoid this effect is given based on the SSFS process. Also, I providean analytical expression to obtain the full spectrum of the TPA of As2Se3 glass. Thiscalculated spectrum is inserted in a numerical simulator to compare the calculated SC toexperiments with better precision. A wide SC spectrum spanning from 1260 to 2200 nm by using a 10 cm long As2Se3 microwire was successfully generated. This was achievedby self-frequency shifting the pump soliton toward longer wavelengths in standard silicafiber before being launched into the microwire.Finally, I present a numerical model to maximize the SC generation in tapered fibers.Using this model, the optimal pulse parameters and the optimum structure of a taperedfiber for a maximum bandwidth of SC are determined. Based on this model, a mid-IR SCsource based on a As2Se3 microwire and a thulium-doped fiber laser is presented. TheSC source generated a continuous spectrum extending from 1400 nm to 2810 nm in a10 cm long As2Se3 microwire from low-energy pulses of 124 pJ. This is the largest SCspectrum obtained in As2Se3 microwires. I discuss the limitations of the absorption bandof OH impurity on extending the generated SC further to the mid-IR regime, and theeffects of water absorption in reducing the energy contained in the spectrum.Dans cette thèse, j'introduis des sources accordables pour l'infrarouge moyen (MIR), basées sur l'auto-décalage fréquentiel de solitons (SSFS) ainsi que la génération de supercontinuum(SC) dans des micro-fils de chalcogénure As2Se3. Premièrement, je présente deux méthodes permettant de maximiser le SSFS dans des micro-fils dont le diamètre varie de manière non-uniforme durant la propagation du soliton. Chaque méthode est composée de deux étapes. La première étape consiste à sélectionner le diamètre d'entrée du micro-fil qui induit un taux maximal d'auto-décalage fréquentiel par unité de longueur. La seconde étape consiste à augmenter graduellement le diamètre du micro-fil dans ladirection de propagation de façon à ce que le soliton se déplaçant en longueur d'ondene subisse que de faibles perturbations induites par la dispersion d'ordre trois et ne se déleste pas de son énergie par la création d'ondes dispersives. Le profil optimisé permetla propagation de solitons de différentes énergies, permettant un déplacement spectralpar auto-décalage fréquentiel sur une plage de 860 nm dans le MIR en utilisant desmicro-fils d'une longueur de 10 cm seulement. Les résultats obtenus sont comparés avecle SSFS générés dans des micro-fils dont le diamètre est constant dans la direction depropagation, afin d'illustrer les améliorations en termes de décalage fréquentiel issues du design de micro-fils non-uniformes. Il s'agit de la première études de SSFS dans desmicro-fils de chalcogénure As2Se3. Deuxièmement, je présente les limitations dues aux effets de l'absorption à deuxphotons (TPA) lors de la génération d'un SC dans le MIR en utilisant des impulsions solitoniques femtosecondes à une longueur d'onde centrale de 1550 nm. Une façon des'affranchir de ces effets, basée sur le procédé de SSFS, est proposée. De plus, je présente une expression analytique permettant d'obtenir le spectre intégral de la TPA intrinsèques aux verres de chalcogénure As2Se3. Ce spectre calculé est inséré dans un simulateur numérique afin de comparer le SC calculé aux expériences réalisées avec une meilleure précision. Un large spectre de SC s'étendant entre 1260 et 2200 nm a pu être généré en utilisant un micro-fil de chalcogénure As2Se3 d'une longueur de 10 cm. Ceci a été rendu possible par l'auto-décalage fréquentiel d'un soliton de pompe vers des longueurs d'ondes plus élevées dans de la fibre de silice standard avant une entrée dans le micro-fil.Finalement, je présente un modèle numérique qui permet de maximiser la génération de SC dans des fibres effilées. De par ce modèle, les paramètres optimaux de l'impulsion d'entrée, ainsi que la structure optimale d'une fibre effilée sont déterminés en vue demaximiser la bande passante du SC induit. En se basant sur ce modèle, une sourceSC pour le MIR basée sur un micro-fil de As2Se3 et un laser à fibre dopée thulium est présentée. La source SC, pompée par des impulsions à basse énergie de 124 pJ, génère un spectre continu s'étendant entre des longueurs d'onde de 1400 nm et 2810 nm dansun micro-fil de chalcogénure As2Se3 d'une longueur de 10 cm. Je décris les limitations induites par la bande d'absorption des impuretés OH. Ces dernières empêchent aux SCinduit de s'étendre plus loin dans le MIR. Les effets de l'absorption de l'eau, réduisant l'énergie contenue dans le spectre, sont aussi discutées.
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Hornstrom, Grete R. "Nutrition knowledge, practice, attitudes, and information sources of Mid-American Conference college softball players". Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1371845.
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Pötzlberger, Markus [Verfasser], i Ferenc [Akademischer Betreuer] Krausz. "High-power femtosecond laser sources for mid-infrared generation / Markus Pötzlberger ; Betreuer: Ferenc Krausz". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2021. http://d-nb.info/1237221625/34.
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Castrillejo, Iridoy Maxi. "Sources and distribution of artificial radionuclides in the oceans: from Fukushima to the Mediterranean sea". Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/457438.
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El objetivo de esta tesis es investigar las fuentes y distribuciones de una serie de radionúclidos artificiales (90Sr, 129I, 134Cs, 137Cs, 236U, 237Np, 239Pu and 240Pu) en dos zonas oceánicas que han recibido un gran impacto debido a actividades humanas.
En primer lugar, el Océano Pacífico, que recibió el impacto de las fugas desde la central nuclear de Fukushima Dai-ichi, inmediatamente después del accidente y en los años siguientes. El estudio se centró en el 90Sr, sobre el cual había poca información a pesar de ser uno de los radionúclidos presentes en mayor cantidad el agua contaminada almacenada en los tanques y la central. En 2013, recolectamos muestras de agua de mar y aguas subterráneas a una distancia de entre 0.8 and ~100 km de la central nuclear. Además, evaluamos el cambio temporal en las concentraciones de 134Cs, 137Cs y 90Sr demostrando la importancia de las contribuciones parciales de cada fuente. Las muestras de agua recolectadas en Septiembre de 2013 presentaban concentraciones de 8.9 ± 0.4 Bq·m-3 de 90Sr, 124 ± 3 Bq·m-3 de 137Cs and 54 ± 1 Bq·m-3 de 134Cs. Estas concentraciones eran significativamente mayores que las medidas antes del accidente nuclear en 2011 debidas a las antiguas pruebas atmosféricas de bombas nucleares: ~1 Bq·m-3, 1-2 Bq·m-3 y negligible, respectivamente. Los resultados confirmaron mediante la relación 137Cs/90Sr la existencia de vertidos continuados de 90Sr desde la central, que estimamos en 2.3-8.5 GB·d-1 en Septiembre de 2013. Si bien loes vertidos continuados son menores que las estimadas para los vertidos que ocurrieron justo después del accidente, existe el riesgo de que sean mayores y por lo tanto, recomendamos continuar con el muestreo y el control de radionúclidos artificiales en el Océano Pacífico.
En segundo lugar, estudiamos el Mar Mediterráneo que recibió los aportes de diferentes fuentes desde 1950: i) a nivel global, las pruebas atmosféricas con bombas nucleares entre 1950 y 1960, y el accidente nuclear de Chernobyl en 1986; ii) a nivel regional, las descargas de agua radioactiva desde la planta de reprocesamiento de Marcoule entre 1958 y 1997; iii) y a nivel local, el accidente de Palomares en 1966. Los resultados muestran que las distribuciones de 129I, 236U, 237Np y 137Cs, estaban controladas por la circulación termohalina. Los resultados también resaltan la importancia relativa de cada una de las fuentes. En particular, estimamos la contaminación derivada de la planta de reprocesamiento nuclear de Marcoule, que fue en comparación con el global fallout, del mismo orden de magnitud para el 236U (10-20 kg) y el 237Np (~7 kg), y dos órdenes de magnitud superior para el 129I (70-90 kg). Marcoule representa entorno al 30% del 237Np presente en el Mar Mediterráneo en 2013. Los cambios temporales en la distribución del 137Cs mostraron la influencia de las fuentes y la circulación oceánica. La relación atómica 240Pu/239Pu era ~0.19 indicando que la fuente principal de este radionúclido en el Mar Mediterráneo es el global fallout. La distribución del 239,240Pu estaba influenciada además, por el proceso de scavenging y la remineralización del material particulado. Uno de los resultados a destacar es el hecho que de las concentraciones e inventarios del plutonio en la cuenca oriental eran menores que en la cuenca occidental. Ello puede ser debido a: i) la mayor importancia del ‘boundary scavenging’ en los sedimentos de la plataforma oriental o ii) a la reducida actividad biológica (que conllevaría una menor exportación del plutonio por las partículas), unida a un mayor transporte lateral por las Levantine Intermediate Waters.This PhD dissertation aimed to understand the sources and distributions of a diverse set of artificial radionuclides (90Sr, 129I, 134Cs, 137Cs, 236U, 237Np, 239Pu and 240Pu) in two contrasting oceanic regions. Firstly, the Pacific Ocean close to Japan, largely impacted by the accident that occurred at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in 2011, which led to the release of radioactive contaminants to the environment immediately after the accident and during the following years. We focused on 90Sr, which was largely understudied despite being of major concern due to its large presence in cooling waters stored in tanks and in the nuclear facility since 2011. We collected seawater, groundwater and surface beach water samples between 0.8 and ~100 km off FDNPP in September 2013, two and a half years after the accident. In this work we also evaluated the temporal evolution of 134Cs, 137Cs and 90Sr concentrations, highlighting the relative importance of various sources in the coast off Japan over time.The radionuclide concentrations in water samples collected in September 2013 were up to 8.9 ± 0.4 Bq·m-3 for 90Sr, 124 ± 3 Bq·m-3 for 137Cs and 54 ± 1 Bq·m-3 for 134Cs in 2013, while their typical concentrations prior to the 2011 accident due to the nuclear tests were ~1 Bq·m-3, 1-2 Bq·m-3 and neglible, respectively. This confirmed the ongoing 90Sr releases from the FDNPP, that we estimated in 2.3-8.5 GB·d-1 in September 2013. Although substantially lower than the rates estimated to have occurred soon after the accident, the continuing releases and the potential larger leaks from the FDNPP evidenced the importance of continuous surveillance of artificial radionuclides in the Pacific Ocean. Secondly, the semi-enclosed Mediterranean Sea, impacted by various sources since the mid-twentieth century: i) on a global scale by atmospheric nuclear weapon tests carried during the 1950s-1960s and the Chernobyl nuclear accident in 1986; ii) at a regional level, by the low level radioactive discharges from the Marcoule nuclear reprocessing plant between 1958 and 1997; iii) and locally by the Palomares accident in 1966. Knowledge on their respective contributions to the presence of 129I, 236U, 237Np and Pu isotopes and on the radionuclide distributions in the Mediterranean Sea was limited or completely unknown. Our data on 129I and 236U showed that their distributions are governed by the thermohaline circulation, and highlighted the importance of constraining each radionuclide source. In particular, we estimated that the contamination derived from the Marcoule nuclear reprocessing plant was likely comparable to that from global fallout for 236U (10-20 kg) and about 2 orders of magnitude larger for 129I (70-90 kg). We also reported for the first time a comprehensive transect of 237Np. The distributions of both 237Np and 137Cs are driven by the circulation of the water masses, as expected for conservative radionuclides. The principal sources of 237Np were found to be global fallout and Marcoule, the later probably contributing to about 30% of the 237Np (~7 kg) present in the Mediterranean Sea in 2013. The distribution of 137Cs showed the influence of inputs and recent changes in circulation. The main source of Pu was confirmed to be global fallout, as shown by the 240Pu/239Pu atom ratios of about 0.18 throughout the Mediterranean Sea. The distribution of 239,240Pu was affected by, in addition to circulation, particle scavenging and remineralization. A notable result of this study was the lower levels of 239,240Pu in the water column of the Eastern Basin than in the Western Basin that were possible due to enchanced boundary scavenging on shelf sediments or the limited scavenging by particles in open waters and enhanced westward transport by water dynamics.
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Berg, Trenton Jeffery. "Compact, mid-infared laser source for remote sensing of gas effluents". Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/berg/BergT1209.pdf.
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Remote sensing of gas effluents in the mid-IR wavelength region from 2 microns to 5 microns is preferred due to strong molecular absorption features (10 to 100 times stronger than in the near-IR) and high-transparency atmospheric windows. Currently, long-range mid-IR remote sensing is inhibited by the lack of suitable laser sources. As a result, frequency conversion in nonlinear optical materials has emerged as a powerful method to produce high-power, tunable, mid-IR light. However, compact, high-power narrowband conversion systems suitable for long-range mid-IR spectroscopy are not commercially available. This thesis describes the development of a high-power, narrowband, tunable, compact, mid-IR laser source for long-range remote sensing of gas effluents. Frequency conversion into the mid-IR is achieved by use of a high-peak-power, compact pump laser and optical parametric generation (OPG) in periodically poled nonlinear crystals. This mid-IR laser system was designed and developed for remote sensing at ranges up to and exceeding 100 m in a compact form factor. Such a laser will fill the current scientific need for a hand-held mid-IR laser source capable of long-range mid-IR spectroscopy. Based on theoretical models and experimental demonstrations a compact mid-IR laser source was developed that emits > 1 mJ broadband pulses in the mid-IR. To narrow the linewidth of the broadband OPG output, optical parametric amplification was demonstrated through seeding of the OPG process with a narrowband, continuous-wave, distributed feedback (DFB) laser. Seeding efficiencies exceeding 35% were demonstrated for 1 mJ of output energy, and efficiencies exceeding 65% were demonstrated at lower energies when the pump beam was spatially filtered. The linewidth of the narrowed mid- IR output was inferred to be < 350 MHz based upon heterodyne measurements conducted at the signal wavelength in the near-IR. This linewidth is well within the FWHM bandwidth of typical mid-IR atmospherically broadened molecular absorption features. The demonstrated mid-IR energies and laser linewidths are predicted to be sufficient for detection of low concentration gas effluents (< 1 ppm) at ranges exceeding 100 m. The developed mid-IR laser source was used to successfully demonstrate differential detection of carbon dioxide (CO 2).
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Gilles, Clément. "Optique intégrée pour sources largement accordables moyen-infrarouge". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS009/document.
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Dans le moyen-infrarouge, les barrettes de lasers à cascade quantique sont d’un grand intérêt pour la réalisation de sources large bande intégrables dans les systèmes de spectroscopie laser. Une excellente finesse spectrale, la présence d’un seul mode spatial et une gamme d’accordabilité large sont ainsi rassemblées sur une seule puce, compacte et intrinsèquement stable. Afin de bénéficier de l’ensemble des longueurs d’onde sur une sortie unique, les défis majeurs résident dans l’association de technologies pour rassembler les différentes sorties en une seule via l’utilisation de circuits photoniques intégrés (CPI). Ce CPI peut être séparé en trois briques élémentaires : une filière de guidage passif, un combineur de longueurs d’onde et un coupleur actif/passif. Pour la mise-en-forme du faisceau, nous reportons la fabrication et la caractérisation de guides d’onde en InP/InGaAs/InP gravés profondément, avec des performances proches de l’état de l’art. Nous fabriquons et caractérisons des multiplexeurs basés sur des réseaux de diffraction intégrés, sur filière InP et SiGe. Un multiplexeur de 60-vers-1 voies couvrant la gamme de 7-8,5 µm est réalisé. Une méthode innovante mettant en œuvre des multiplexeurs inter-digités et fonctionnant sur trois ordres de diffraction est démontrée. Finalement, nous réalisons des barrettes de laser à cascade quantique sur InP et sur silicium. Un coupleur adiabatique est dimensionné, fabriqué et caractérisé pour associer efficacement les guides actifs et passifs. Des intégrations de types hétérogène et hybride sont envisagées, avec la première démonstration d’une source accordable utilisant une barrette de lasers et un multiplexeur InPIn the mid-infrared, arrays of distributed feedback quantum cascade lasers have been developed as a serious alternative to obtain extended wavelength operation range of laser-based gas sensing systems. Narrow-linewidth, single mode operation and wide tunability are then gathered together on a single chip with high compactness and intrinsic stability. In order to benefit from this extended wavelength range in a single output beam, the key challenge resides in the combination of different technologies to merge the output of different sources via the use of mid-IR photonic integrated circuits (PIC). The PIC can be split into three main blocks: the passive waveguide platform, the beam combiner and the active/passive coupler. For beam handling and guiding, we report fabrication and characterization of deeply etched InP/InGaAs/InP waveguides with state of the art performances. We fabricate and characterize multiplexers based on echelle and arrayed waveguide gratings on InP and SiGe platforms. A 60-to-1 spectral multiplexer operating in the 7-to-8.5 µm range is demonstrated. An advanced multiplexing scheme using interleaved and cross-order operations is also exposed. Finally, we realize quantum cascade laser arrays on InP and silicon. We design, fabricate and characterize an adiabatic coupler to efficiently and monolithically integrate active and passive waveguides. Heterogenous and hybrid integration are also considered with the demonstration of a tunable source using laser array and InP-based multiplexer
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Parsa, Shahrzad. "High-power fiber-laser-pumped picosecond nonlinear optical sources from the near- to mid-infrared". Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/620786.
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Ultrafast picosecond coherent sources in the near-to-mid-infrared (IR) spectral range are of great interest for a variety of applications such as pump-probe spectroscopy, remote sensing, photobiology and novel upconversion imaging techniques. Nonlinear optics, and in particular nonlinear frequency conversion techniques, offer an efficient and effective approach towards the realization of sources emitting such radiation, as nowadays, nonlinear frequency conversion technologies are recognised to be viable and reliable sources of laser radiation with broad wavelength tunability and power scalability, without the need of cryogenic cooling.
In this thesis, we have demonstrated high-power, high-repetition-rate picosecond sources based on nonlinear frequency conversion processes through optical parametric oscillators (OPOs) and difference-frequency-generation (DFG), in order to cover the near- to mid-IR wavelength region.
We have developed a stable, high-repetition-rate picosecond rapidly tunable OPO based on fan-out designed grating periods in PPKTP nonlinear crystal. The OPO is synchronously pumped by a mode-locked frequency-doubled Yb-fiber laser in the green at 532 nm, and can provide stable and high-power radiation which is rapidly tunable from 749-962 nm in the signal and from 1189-1838 nm in the idler, at room temperature.
Further, we have demonstrated what we believe to be the first tunable high-repetition-rate picosecond source based on OP-GaP crystal in the mid-IR. Using a single-pass DFG between a mode-locked Yb-fiber laser at 1064 nm and the tunable output from a picosecond MgO:sPPLT OPO synchronously pumped by the same laser, the source generated continuous tunable radiation across 3040-3132 nm in the mid-IR at the repetition rate of ~80 MHz, in good beam quality.
Additionally, we have also presented the first high-power, high-beam-quality, idler-resonant picosecond OPO based on a multi-grating MgO:PPLN crystal tunable across 2100-4000 nm in the mid-IR. The OPO provided as much as 3.5 W of mid-IR radiation with M2 values to be better than 1.8 in both horizontal and vertical directionsLas fuentes coherentes de picosegundos ultrarrápidos en el rango espectral de infrarrojo cercano a infrarrojo medio (IR) son de gran interés para una amplia variedad de aplicaciones tales como pump-probe espectroscopia, la teledetección, la fotobiología y las nuevas técnicas de upconversion imaging. La óptica no lineal, y en particular las técnicas de conversión de frecuencia no lineal, ofrecen un enfoque eficiente y eficaz para la realización de fuentes que emiten tales radiaciones, ya que hoy en día, las fuentes basadas en la conversión de frecuencia no lineal son fuentes viables y fiables de emisión de radiaciones láser con amplia sintonía de longitud de onda y escalabilidad de potencia, sin necesidad de refrigeración criogénica. En esta tesis, hemos demostrado fuentes de picosegundos de alta potencia y alta tasa de repetición basadas en procesos de conversión de frecuencia no lineales a través de osciladores ópticos paramétricos (OPO) y generación de frecuencias de diferencia (DFG) para cubrir la región de longitud de onda de IR cercano a IR medio del espectro electromagnético. Hemos desarrollado una fuente de picosegundos estable, de alta tasa de repetición, rápidamente sintonizable, basado en un cristal PPKTP con períodos de rejilla diseñados en forma de abanico. El OPO, es bombeado sincrónicamente por un mode-locked láser de fibra de Yb, doblado en frecuencia para generar verde a 532 nm, que proporciona radiación estable y de alta potencia rápidamente sintonizable de 749-962 nm en el signal y de 1189-1838 nm en el idler, a temperatura ambiente. Además, hemos demostrado lo que creemos que es la primera fuente de picosegundos sintonizable con alta tasa de repetición basada en el cristal OP-GaP en el IR medio. Usando una DFG de un solo paso entre un mode-locked láser de fibra de Yb a 1064 nm y la salida ajustable de un OPO de picosegundo basado en un cristal de MgO:sPPLT bombeado sincrónicamente por el mismo láser, la fuente generó radiación sintonizable de 3040-3132 nm en el medio-IR a la velocidad de repetición de ~80 MHz, con buena calidad de haz. Además, también presentamos el primer OPO de picosegundos de alta potencia y buena calidad de haz, con resonancia del idler, basado en un cristal MgO:PPLN de rejilla múltiple sintonizable a lo largo de 2100-4000 nm en el IR medio. El OPO proporcionó hasta 3.5 W de radiación de IR medio con valores de M2 mejores que 1.8 tanto en dirección horizontal como vertical
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Kedenburg, Stefan [Verfasser], i Harald [Akademischer Betreuer] Giessen. "Near- and mid-infrared supercontinuum sources with MHz repetition rates / Stefan Kedenburg ; Betreuer: Harald Giessen". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2017. http://d-nb.info/1132134536/34.
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Krier, Susan Elaine. "Light sources for the mid-infrared spectral region based on narrow gap III-V alloys". Thesis, Lancaster University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404257.
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Tandeo, Pierre. "Modélisation spatio-temporelle d’une variable quantitative à partir de données multi-sources : Application à la température de surface des océans". Rennes, Agrocampus Ouest, 2010. https://tel.archives-ouvertes.fr/tel-00582679.
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Ce travail de thèse porte sur une variable océanographique importante dans le suivi du climat : la température de surface des océans. Au niveau global, les observations de cette température sont fournies principalement par des radiomètres embarqués sur des satellites. Afin de traiter ce flux important de données, un traitement statistique s’impose dans le but de synthétiser l’information en des cartes globales et quotidiennes de notre variable d’intérêt. Pour ce faire, nous proposons un modèle linéaire de type espace-d’état avec des erreurs Gaussiennes. Nous commençons par présenter ce modèle sur des données issues de séries temporelles ayant un échantillonnage irrégulier. Suit un travail d’inférence avec la mise en place d’un schéma d’estimation des paramètres, basé sur la combinaison d’une méthode des moments et du maximum de vraisemblance au travers de l’algorithme EM et des probabilités de filtrage et lissage de Kalman. Nous appliquons enfin cette méthodologie pour estimer les variances d’erreurs et le paramètre de corrélation temporelle à tout l’océan Atlantique. Nous ajoutons ensuite la composante spatiale et proposons une structure d’ordre deux, séparable, basée sur le produit d’une covariance temporelle et d’une covariance spatiale anisotrope. Les paramètres de cette dernière sont estimés sur l’océan Atlantique à partir de techniques géostatistiques usuelles et forment un atlas pertinent pour les océanographes. Finalement, nous montrons que l’apport de l’information spatiale augmente le pouvoir prédictif du modèleIn this thesis, an important oceanographic variable for the monitoring of the climate is studied: the sea surface temperature. At the global level, this variable is observed along the ocean by several remote sensed sources. In order to treat all this information, statistical methods are used to summarize our variable of interest in global daily map. For that purpose, a state-space linear model with Gaussian error is suggested. We begin to introduce this model on data resulting from having an irregular sampling. Then, we work on the estimation of the parameters. This is based on the combination of the method of moments and the maximum likelihood estimates, with the study of the EM algorithm and the Kalman recursions. Finally, this methodology is applied to estimate the variance of errors and the temporal correlation parameter to the Atlantic ocean. We add the spatial component and propose a separable second order structure, based on the product of a temporal covariance and a spatial anisotropic covariance. According to usual geostatistical methods, the parameters of this covariance are estimated on the Atlantic ocean and form a relevant atlas for the oceanographers. Finally, we show that the contribution of the spatial information increases the predictive behaviour of the model
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Hung, Hazel S. S. "An adaptive mid-infrared ultrashort pulse source for applications in coherent control". Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/340806/.
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An adaptive mid-infrared (MIR) ultrashort pulse source is investigated for application to the coherent control of molecules. The MIR regime will allow access to vibrational modes of common organic bonds, and ultrashort pulse durations should enable the required interaction to occur before the energy is redistributed throughout the molecule. By using the molecular system as part of an adaptive learning loop, one can deliver the desired MIR pulse without the need for prior lengthy calculations to solve the Hamiltonian. The adaptive MIR pulse shaper is presented as a feasibility study in this thesis. It involves shaping a near-infrared (NIR) pulse using a spatial light modulator in a phase-only pulse shaper. The shaped NIR pulse is then transferred to the MIR via a synchronously pumped optical parametric oscillator (SPOPO), which is consequently measured using a nonlinear detector whose signal is used as the feedback parameter to be optimised. Using a global optimisation algorithm, initial experiments demonstrated adaptive MIR pulse shaping, achieving pulse compression and double pulse generation. The transfer of the pulse shape from the NIR to the MIR in the SPOPO however, is non-trivial and is discussed in detail, both numerically and experimentally, in this thesis. The results show that parameters such as the signal pulse bandwidth, temporal walk-off of the interacting pulses, signal gain, pump depletion, and group velocity dispersion should be considered when high fidelity transfer is required. It is also shown that, for an SPOPO based on periodically poled LiNbO3 high-fidelity transfer is possible for wavelengths centred around 3.5 μm with a tunability of ±0.5 μm. The investigation then progresses to the femtosecond regime where the demonstration of coherent control experiments becomes more accessible. Using a fibre-based chirped pulse amplification system, which is an attractive pump source for the SPOPO, adaptive pulse shaping is demonstrated, showing significant improvement in the quality of the 500 fs source at high pulse energies of 65 μJ, as a result of the learning loop. Thus the individual components to make the adaptive MIR ultrashort pulse shaping system have all been demonstrated; namely the adaptive shaping of MIR pulses via an SPOPO, the high-fidelity transfer of NIR pump pulses to the MIR in an SPOPO, and the femtosecond NIR pump source.
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Constant, Mel. "Source, transfert et devenir des microplastiques (MPs) en mer Méditerranée Nord-Occidentale". Thesis, Perpignan, 2018. http://www.theses.fr/2018PERP0057/document.
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Les déchets plastiques et les produits issus de leurs fragmentations (microplastiques ou « MP », <5mm) représentent une menace globale et persistante pour l'ensemble des écosystèmes marins, du fait de leur facilité d'ingestion par une grande diversité d'espèces marines. La mer Méditerranée, de part sa nature semi-fermée et son littoral anthropisé, est très impactée par cette pollution. Cette thèse a pour objectif de mieux comprendre l'origine et le devenir des MP en mer, et ce, par la mise en place d'une stratégie d’échantillonnage le long du continuum terre-mer, i.e. des sources continentales aux récepteurs marins finaux. Cette approche holistique a été appliquée à l'échelle locale du golfe du Lion (Nord-Ouest de la Méditerranée) à l’ensemble des compartiments côtiers. Les MP ont été retrouvés dans toutes les matrices étudiées (eau, sédiment, dépôtatmosphérique et tissus biologiques) dans des quantités très variables à la fois dans les compartiments et entre les compartiments. Aucune sélection qualitative (forme, taille, polymère et couleur) majeure ne semble s'opérer lors du transfert des MP d'un compartiment à l'autre, et la majorité des MP sont des fibres. Quantitativement, la concentration des MP varie à des échelles temporelles et spatiales très courtes (<1 heure et <1 kilomètre). Si aucune relation claire entre les concentrations en MP et les forçages environnementaux (e.g. précipitation, débit des fleuves, vents, etc.) n'a été observée, les événements de précipitation semblent influencer grandement les quantités de MP transférées entre les compartiments. En extrapolant nos résultats aux bassins-versants du golfe du Lion, 30 ± 20 tonnes de MP se déposeraient via l'atmosphère sur les zones urbainescôtières et 7 ± 10 tonnes de MP seraient transportées par les fleuves vers la Méditerranée, chaque année. L'extrapolation des quantités de MP dans les compartiments marins, semble indiquer que la surface de la mer et les plages ne sont que des compartiments transitoires (< 1 tonne), tandis que les sédiments et la colonne d'eau sont potentiellement plus impactés (jusqu'à 350 tonnes pour les sédiments). De nouvelles données sont nécessaires pour la colonne d'eau et les sédiments pourconfirmer cette hypothèse, mais les résultats laissent penser qu'ils pourraient avoir un rôle majeur dans le stockage des MPAnthropogenic litter, particularly plastic litter and their fragments (microplastics or “MPs”; < 5 mm) represent a highly pervasive and persistent global threat to marine ecosystems, as they can be ingested by a wide range of marine species. As a landlocked sea with a high population density, the Mediterranean Sea is highly exposed to marine litter pollution. This thesis aims tounderstand the origin and the future of marine MPs thanks to a holistic approach from terrestrial sources to marine sinks. This strategy was applied at the regional scale of the Gulf of Lion (Northwestern Mediterranean Sea) on all coastal compartments. MPs were observed in every studied matrices (water, sediment, atmospheric fallout) with a high variability within and betweenthe different compartments. No significant qualitative trend seems to occur during the transfer of MPs between compartments and fibers were the most abundant shape found in samples. MP concentrations changed at a short spatial and temporal scale (< 1 hour and < 1 kilometer), overlaying other variabilities (i.e. seasonal or between sites). If no obvious relationship betweenexternal forcing (e.g. precipitations, river flow rates, winds) and MP concentrations was observed, rainfall events seemed to have an important impact on the amount of MPs transferred into the sea. Extrapolating our results to the whole Gulf of Lion watersheds, 30 ± 20 tons of MPs would settle on urban areas and 7 ± 10 tons would be supplied by rivers into the Mediterranean Sea every year. The extrapolation of MP quantities within marine environments seems to indicate that the sea surface and beaches are only transitory compartments (<1 ton) whereas sea floor and water column couldbe more impacted (up to 350 tons for marine sediment). New data on water column and marine sediments are needed to confirm this hypothesis, but those results suggest that both latter compartments could be major sinks for marine MPs
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Devi, Kavita. "Continuous-wave optical parametric oscillators and frequency conversion sources from the ultraviolet to the mid-infrared". Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/130392.
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High-power, continuous-wave (cw) optical parametric oscillators (OPOs), from the ultraviolet (UV) and visible to the near- and mid-infrared (IR) wavelength range, are of interest for a variety of applications such as spectroscopy, trace-gas detection and remote sensing. As such, it is desired to investigate OPOs and different frequency conversion techniques, to cover the spectral regions that are inaccessible to lasers, and that too in a compact and low-cost design.
This thesis presents the development of high-power cw OPOs, and frequency conversion sources, spanning the UV to mid-IR spectral range, employing different designs, experimental configurations and nonlinear crystals, making them compact and cost-effective. Commercial high-power cw lasers at 1940 nm, 1064 nm and 532 nm have been exploited as the pump sources, in the work presented in this thesis.
We have demonstrated a fiber-based cw source at 970 nm, in a simple and practical design. Using direct single-pass second-harmonic-generation (SHG), 13.1 W of output power at 970 nm has been generated in a high-beam-quality,
narrow-linewidth, linearly-polarized beam. Further, a technique based on the use of an antiresonant ring (ARR) interferometer for the attainment of optimum output coupling in a cw singly-resonant OPO has been investigated. The technique was deployed in a Yb-fiber-laser-pumped cw OPO based on MgO:PPLN. To extend the tunability of the 1-µm-pumped OPO from the mid-IR to near-IR, SHG of the intracavity signal has been performed in fanout-grating MgO:sPPLT. This compact cw source, tunable across 775¿807 nm, provides >3 W of near-infrared power across 56% of SHG tuning range, in high spatial beam quality. We have also generated output in the UV, down to 355 nm, using single-pass configuration based on sum-frequency-generation of fundamental at 1064 nm and the generated SHG at 532 nm, in BiB3O6. Further, we demonstrated an architecture comprising two cw OPOs coupled together with an ARR interferometer, generating two pairs of signal and idler wavelengths, that can be independently and arbitrarily tuned to indefinitely close spacing, through degeneracy, and beyond, across the wavelength range of 870-1370 nm. The OPOs, based on identical MgO:sPPLT crystals, were pumped by a single cw laser at 532 nm. On the other hand, we also demonstrated active mode-locking of cw OPOs using direct low-frequency electrooptic phase-modulation (EOM), opening up the possibility of avoiding the need for ultrafast laser sources and synchronous pumping. We have generated picosecond pulses in doubly- and singly-resonant configuration. Also, a technique based on the deployment of the EOM in combination with an ARR interferometer internal to the cw OPO has been investigated for active modelocking.
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Archipovaite, Giedre Marija. "High energy and high repetition rate parametric sources in the mid- wavelength Infrared and their applications". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0158/document.
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Les sources lasers à impulsions ultracourtes de forte puissance dans la région spectrale du proche à moyen infrarouge sont très demandées pour la physique des champs forts dans les atomes, les molécules et la matière condensée. D’après le modèle en trois étapes [1], l’énergie coupée des harmoniques élevées générées varie comme I×λ2. Cela favorise les longueurs d’onde plus longues pour générer des photons XUV plus énergétiques, et potentiellement des impulsions attosecondes plus courtes. Malheureusement, l’extension de l’énergie des photons se fait au prix d’une diminution de l’efficacité en λ−5,5 [2]. La disponibilité d’un système laser à haute cadence est un atout majeur pour palier aux problèmes d’efficacité et produire des flux de photons élevés. Même s’il existe quelques matériaux de gain laser adaptés à la génération d’impulsions femtoseconde intense dans la région spectrale infrarouge intermédiaire, l’amélioration globale du taux de répétition, de la durée et de la puissance des impulsions sont encore des défis [3, 4]. Ainsi, les systèmes paramétriques basés sur un mélange non linéaire à trois ondes sont une alternative intéressante pour générer les impulsions ultracourtes requises pour ce type d’expériences. Actuellement, les systèmes paramétriques à haute puissance dans l’infrarouge moyen ne peuvent pas atteindre les intensités requises pour générer des harmoniques dans le gaz. Cependant, ces sources sont des moteurs intéressants pour la génération d’harmonique (HHG) dans les solides, qui nécessitent des intensités sur cible plus faibles. Par ailleurs, les systèmes à haute énergie, mais à taux de répétition plus bas, sont capables de générer des impulsions suffisamment énergétiques pour les expériences HHG dans le gaz. Cependant, l’efficacité globale de ces sources est encore faible. En fonction de l’énergie harmonique requise, le rayonnement peut être généré efficacement par des lasers NIR post-comprimés.Cette thèse décrit le développement des sources MWIR et leurs applications en physique des champs forts. Nous avons choisi d’étudier des sources paramétriques pilotées par un laser à pompe CPA de puissance moyenne élevée et par un système laser à grande énergie Yb: CaF2. Les impulsions MWIR générées sont ensuite utilisées pour sonder l’interaction du matériau laser à travers HHG dans les solides et les gazUltrashort pulse light sources in the near- to mid-wavelength infrared spectral region are in high demand for strong field physics in atoms, molecules and condensed matter. According to the three step model [1], the energy cut off of generated high harmonics scales as I×λ2, which favors longer driving wavelengths in order to generate more energetic XUV photons, and potentially shorter attosecond, soft X-ray pulses. Unfortunately, photon energy extensionis at the cost of an efficiency drop scaling as λ−5.5 [2]. The availability of a high-repetitionrate laser system is paramount to mitigate the efficiency issues and still produce high photon fluxes. Even though there are only a few laser gain media suitable for intense femtosecond pulse generation in the mid-IR spectral region, the overall scalability of the pulse repetition rate, the duration and power are still a challenge [3, 4]. Thus, parametric systems based on a nonlinear three wave-mixing, are an attractive alternative to generate the required ultrashort pulses for those experiments. Currently high power middle infrared parametric systems can’t reach the required intensities to reliably drive high harmonic generation (HHG) in gas. However, these sources are attractive drivers for HHG in solids, which requires lower intensities on the target. On the other hand, high energy, but lower repetition rate systems arecapable of generating energetic pulses for HHG experiments in gas. However, the overall efficiency of those drivers is still low. Depending on the required harmonics energy, the XUV could be efficiently generated by post-compressed NIR lasers.This thesis describes the development of MWIR sources and their applications in strong field physics. We have chosen to investigate parametric sources driven by high average power fiber CPA pump laser and by high energy Yb:CaF2 bulk laser system. The generated MWIR few cycle pulses are then used to probe laser material interaction through HHG in solids and gas
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Jargot, Gaëtan. "High-repetition rate CEP-stable few-cycle OPCPA sources in the short wavelength infrared/mid-infrared". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLO020.
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Résumé : La génération d’impulsions de quelques cycles optiques stabilisées en CEP dans le moyen infrarouge utilisant la technique d’amplification paramétrique optique à fort taux de répétition est d’un grand intérêt pour diverses études de dynamiques ultra-brèves. Les travaux de cette thèse sont directement inscrits dans ce cadre. Nous décrivons un système émettant des impulsions dont le spectre est centré à 2.1 µm avec une durée de 19.5 fs et une énergie de 31 µJ opérant à 10 kHz avec une stabilité RMS de 0.54 %. Ce système se distingue de l’état de l’art par la mise en œuvre d’une technique de différence de fréquence en ligne permettant d’obtenir une stabilité de la CEP tir-à-tir de 107 mrad pendant quatre heures. De plus cette thèse à permis le dévelopement d’un dispositf émettant des impulsions de quelques cycles optiques à 1.55 µm opérant à haut taux de répétition (125 kHz). Ce système est le résultat de l’assemblage d’un amplificateur paramétrique optique et d’un systéme de compression non-lineaire dans une cellule multi-passage. La propagation non linéaire périodique dans la cellule en régime de dispersion anormale permet une compression solitonique, tout en moyennant les effets spatiaux de la nonlinéarité sur le faisceau. Nous démontrons ainsi l’autocompression d’impulsions initiales de 19 µJ 63 fs vers des impulsions en sortie de 14 µJ 22 fsAbstract : The generation of carrier envelope phase (CEP) stable few-cycle pulses in the SWIR/Mid-IR using optical parametric chirped pulse amplification (OPCPA) at high repetition rate is of great interest for several applications in ultrafast dynamics. During this thesis the work was primarily focused on the development of OPCPA sources for attosecond science. We present an OPCPA operating at 2.1 µm delivering 19.5 fs pules duration with an energy of 31 µJ at 10 kHz with a RMS energy stability of 0.54 %. An original architecture using an all-inline difference frequency generation stage allows performances beyond the state of the art in terms of CEP stability. We report RMS CEP fluctuations of 107 mrad RMS measured shot-to-shot over four hours. On another hand, the development of a high repetition rate (125 kHz) OPCPA coupled with an innovative nonlinear compression scheme is described. The OPCPA provides pulses centered at 1.55 µm, with a pulse duration of 63 fs with an energy of 19 µJ after compression. Then a nonlinear compression stage based on a soliton dynamics in a multipass cell is implemented. The periodic propagation inside the cell allows to retain the temporal nonlinear effects, while the spatial nonlinear effects are washed out by the distributed nature of the nonlinearity over a large number of passes. We report the self-compression of 63 fs pulse at 1.5 µm down to 22 fs with an energy of 14 µJ