Dissertations / Theses on the topic 'Faisceau cohérent'
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Ayanides, Jean-Philippe. "Etude statistique de la propagation non-linéaire d'un faisceau laser partiellement cohérent." Palaiseau, Ecole polytechnique, 2001. http://www.theses.fr/2001EPXX0034.
Masiello, Fabio. "Diffraction et imagerie aux rayons X en utilisant un faisceau cohérent : applications aux optiques rayons X et au cristaux comportant des hétérogénéités de phase." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00609216.
Pavel, Mihai-Cosmin. "Moduli spaces of semistable sheaves." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0125.
In this thesis we construct moduli spaces of semistable sheaves over a complex smooth projective variety X, endowed with a fixed polarization sheaf{O}_X(1). Our approach is based on ideas of Le Potier and Jun Li, who independently constructed moduli spaces of slope-semistable torsion-free sheaves over (projective) surfaces. Their spaces are closely related, via the Kobayashi-Hitchin correspondence, to the so-called Donaldson-Uhlenbeck compactification in gauge theory. Here, however, we are mainly interested in the algebraical aspects of their work. In a restrictive sense, this thesis generalizes their construction to higher dimensional pure sheaves, whose support scheme might be singular. First we introduce a notion of stability for pure coherent sheaves of dimension d on X, which lies between slope- and Gieseker-stability. This is defined with respect to the Hilbert polynomial of the sheaf, truncated down to a certain degree. We call it ell-(semi)stability, where ell marks the level of truncation. In particular, this recovers the classical notion of slope-stability for ell =1 and of Gieseker-stability for ell = d. Our construction uses as main ingredient a restriction theorem for (semi)stability, saying that the restriction of an ell-semistable (or ell-stable) sheaf to a general divisor D in |sheaf{O}_X(a)| of sufficiently large degree in X is again ell-semistable (respectively ell-stable). In this regard, in Chapter~ef{ch:RestrictionTheorems} we prove several restriction theorems for pure sheaves (see Theorems~ef{thm:GiesekerRestriction},ef{thm:restrictionStable} and ef{thm:ThmC}). The methods employed in the proofs permit us to give statements in arbitrary characteristic. Furthermore, our results generalize the restriction theorems of Mehta and Ramanathan for slope-(semi)stability, and they apply in particular to Gieseker-semistable sheaves. Before we give the construction, we take a short detour to generalize the classical Iitaka fibration to the equivariant setting. Given this, we construct projective moduli spaces of ell-semistable sheaves in higher dimensions as certain equivariant Iitaka fibrations (see Theorem~ef{thm:mainThm}). Our construction is new in the literature when 1
Gamelin, Alexis. "Collective effects in a transient microbunching regime and ion cloud mitigation in ThomX." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS276/document.
The thesis is focused on the study of collective effects in a 50 MeV electron storage ring, ThomX, in the absence of synchrotron radiation damping and of longitudinal matching. This thesis is divided in two distinct parts. The first part corresponds to the design of the impedance model (geometric and resistive wakefields, coherent synchrotron radiation) of the storage ring in order to simulate the beam dynamics. The geometric impedance model of the storage ring was obtained via simulation of the individual elements and was checked using wire measurements on prototypes. The coherent synchrotron radiation was simulated taking into account a rectangular vacuum chamber. Beam dynamics simulations, from the RF gun cathode to the storage ring, including collective effects are presented. The simulations are used to optimise the beam dynamics in the storage ring in the micro-bunching regime. The second part is the study of the ion cloud produced by the ionisation of the residual vacuum molecules and the optimisation of the ion clearing techniques. The longitudinal ion accumulation points and the trapping in magnetic fields are both studied analytically and by using a tracking code developed for this purpose. Clearing electrodes and clearing gaps are simulated and optimised using this code and the strategy chosen for the limitation of ion induced effects is described. Finally, the effect of multi-ionisation and ion dissociation is taken into account and the ion effect on the electron beam is estimated
Macor, Alessandro. "D'un faisceau test à l'auto-cohérence dans l'interaction onde-particule." Aix-Marseille 1, 2007. http://www.theses.fr/2007AIX11016.
Samokhin, Alexander. "Les catégories dérivées des faisceaux cohérents sur certaines variétés de Fano." Paris 13, 2005. http://www.theses.fr/2005PA132025.
Mocella, Vito. "Cohérence d'un faisceau synchrotron et théorie dynamique de la diffraction : simulations et expériences." Grenoble 1, 1999. http://www.theses.fr/1999GRE10088.
Bellanger, Cindy. "Techniques collectives pour la recombinaison cohérente d'un grand nombre de fibres laser." Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00498684.
Paboeuf, David. "Combinaison cohérente de diodes laser de luminance élevée en cavité externe." Paris 11, 2009. http://www.theses.fr/2009PA112161.
The constant and growing demand for compact and efficient laser sources leads to explore new architectures aiming at increasing the he output powers of laser diodes. The most promising solution consists in utilizing several moderate-power identical lasers in parallel. It is then necessary to induce a constant phase relationship between the lasers to maintain the spatial beam quality. We present a theoretical and experimental study of the passive phase locking of an array of high-power diode lasers. We take benefit of the angular and spectral filtering properties of volume Bragg gratings in an external cavity. Two solutions have been considered : the first one uses the self-imaging Talbot effect and the second one consists in a selective angular filtering of the array emission. A theoretical model aiming at determining the modal behaviour of those two cavities has been realized. Moreover, concerning the Talbot cavity, in collaboration with the university of Nottingham, a cavity model taking into account the internal properties of the diode lasers has also been used. Experimentally, several cavity setups adapted to different array geometries have been investigated. Each of them achieved a coherent emission. We show that the use of volume Bragg gratings inside the cavity improve both the coherence and the spectrum of the lasers. Finally, we present an original solution using phase filters to convert the multilobed beam from the laser cavity into a Gaussian beam profile
Guillot, Julien. "Laser à fibres auto-organisé à faisceaux multiples couplés." Limoges, 2011. https://aurore.unilim.fr/theses/nxfile/default/9efcf767-6daf-4baf-95f8-8f49d53d2ebb/blobholder:0/2011LIMO4003.pdf.
This document deals with passive coherent combining of fiber lasers. The laser architecture explored is a configuration with multiple emitters where the beam phase-locking is based on an intracavity spatial frequency filtering and self-organization properties of lasers. The multiple beams are combined only in the far field. The experimental results show this phasing technique is scalable to high power levels. Moreover, an experimental study demonstrates that this technique have a rapid dynamic phase-locking. However, a numerical and experimental study show this passive phasing technique can combined only a dozen of beams effectively. So, a new architecture with multiple feedbacks has been proposed. The numerical results are very promising and reveal a very significant contribution of this new architecture
Michel, Pierre A. "Perte de la cohérence d'un faisceau laser intense lors de sa propagation dans un plasma." Palaiseau, Ecole polytechnique, 2003. http://www.theses.fr/2003EPXX0031.
Drebot, Illya. "Electron beam dynamics with and without Compton back scattering." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00920424.
Hosgood, Timothy. "Chern classes of coherent analytic sheaves : a simplicial approach." Thesis, Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0184.
The aim of this thesis is to review and improve upon an unpublished thesis by Green, whose goal was to construct Chern classes of coherent analytic sheaves in de Rham cohomology that respect the Hodge filtration. The second part of this thesis is dedicated to the construction of a categorical enrichment of the bounded derived category of complexes of coherent sheaves on an arbitrary complex manifold: the objects are `simplicial' vector bundles endowed with a certain type of simplicial connection. This construction uses the theory of twisting cochains, developed in this setting by O'Brian, Toledo, and Tong. The first part is dedicated to defining a categorical lift of the Chern character in de Rham cohomology that respects the Hodge filtration, and for this we use the categorical model mentioned above. This construction can be undertaken by adapting classical Chern-Weil theory to the simplicial setting, using Dupont's theory of fibre integration
Grech, Mickael. "Modifications des propriétés de cohérence des faisceaux laser dans les plasmas de fusion par confinement inertiel." Bordeaux 1, 2007. http://www.theses.fr/2007BOR13387.
Michel, Gilles. "Évaluation des algorithmes théoriques de traitement du signal appliqués aux micropotentiels des activités électrocardiologiques : nouveau concept d'analyse par cohérence temporelle." Nice, 1990. http://www.theses.fr/1990NICE4408.
Perego, Arvid. "Un théorème de Gabriel pour les faisceaux cohérents tordues et Groupe de Picard et 2-factorialité des exemples de O'Grady de variétés irréductibles symplectiques." Phd thesis, Université de Nantes, 2008. http://tel.archives-ouvertes.fr/tel-00340585.
Rossé, B. "Détection $\gamma$ et faisceaux radioactifs : recherche de noyaux exotiques très déformés." Phd thesis, Université Claude Bernard - Lyon I, 2006. http://tel.archives-ouvertes.fr/tel-00120476.
Les rayonnements γ ont été détectés par le multidétecteur EXOGAM, composé de « clovers » segmentés de germanium pour lesquels une nouvelle méthode de calibration en énergie des segments a été développée. Pour extraire les événements de fusion-évaporation d'un fort bruit de fond lié à la radioactivité du faisceau, nous avons couplé EXOGAM avec le détecteur de particules chargées légères DIAMANT ainsi qu'avec le spectromètre de grande acceptance VAMOS, utilisé pour la première fois pour la détection de résidus d'évaporation.
L'analyse minutieuse de l'ensemble des données nous a permis de montrer que le couplage EXOGAM + DIAMANT + VAMOS est opérationnel et nécessaire pour l'étude de la structure des noyaux de cette région. De plus, nous avons pu mettre en évidence la première transition γ du noyau très exotique impair-impair 130Pm. Les résultats ont été interprétés à partir de calculs théoriques microscopiques auto-cohérents statiques et dynamiques effectués en collaboration avec les physiciens du groupe de Physique Théorique de l'IPN Lyon.
Perego, Arvid. "Un théorème de Gabriel pour les faisceaux cohérents tordus et groupe de Picard et 2-factorialité des exemples de O'Grady de variétés irréductibles symplectiques." Nantes, 2008. http://www.theses.fr/2008NANT2057.
This PhD thesis is divided in two parts : in the firs one, we present a generalization of Gabriel's Theorem on coherent sheaves to twisted coherent sheaves : more precisely, we show that any Noetherian scheme X can be reconstructed from its abelian category Coh(X; α) of coherent sheaves twisted by an element α in the cohomological Brauer group de X. In the second part we study the two moduli spaces M10 and M6 introduced by O'Grady, which he uses to obtain his two new examples of irreducible symplectic varieties in dimension 10 and 6. We calculate the Picard group of M10 and M6, and we show that these two varieties are not locally factorial, but 2-factorial. This is done using the results obtained by Rapagnetta on the cohomology and the Beauville-Bogomolov form of M10 and M6, and studying the properties of the Le Potier's morphism in these two cases
Minard, Benoît. "Développement et validation d'un outil basé sur l'acoustique géométrique pour le diagnostic du bruit de nacelle." Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6196.
Surville, Julien. "Développement et mise en œuvre de diagnostics spécifiques pour l'analyse d'une figure de tavelures obtenue par lissage optique." Bordeaux 1, 2005. http://www.theses.fr/2005BOR13122.
We have developed three main optical methods to study of the speckles generated bya smoothed laser source. The first method addresses the measurement of the temporal andspatial correlation functions of the source, with a modified Michelson interferometer. Thesecond one is a pump-probe technique created to" take a picture" of a speckle pattern generatedat a given time. And the third one is an evolution of the second method dedicated to time-frequency coding, thanks to a frequency chirped probe pulse. Thus, the speckles can be followedin time and their motion can be described. According to these three methods, the average sizeand duration of the speckles can be measured. It is also possible to measure the size and theduration of each of them and mostly their velocity in a given direction. All the results obtainedhave been confronted to the different existing theories
Philippet, Laurent. "Amplification de l'énergie d'une source VUV cohérente à 125 nm dans une plume d'ablation de mercure." Phd thesis, Paris 13, 2009. http://www.theses.fr/2009PA132038.
This work is devoted to the study of an original technique based on laser ablation of liquid mercury in order to enhance the conversion efficiency of a coherent VUV source at 125 nm. The radiation is obtained by two-photon resonant sum frequency (6s 1S0 → 7s 1S0) in mercury vapor at room temperature. The experimental parameters such as the plume geometry, the energy of the fundamental beams, the laser ablation fluence and the pressure of a buffer gas (here argon which allows to control the plume expansion) have been carefully optimized and led to an amplification of one order of magnitude (two orders of magnitude when intensities are reduced) and an energy of 250 nJ. For a better understanding of the physical phenomena involved in the nonlinear process, a complet characterization of the plume has been set up thanks to time resolved fast photography and spectral analysis of plume emission. The plume luminescence and the two- photon laser induced fluorescence (on the line 6s 1S0 → 7s 1S0) gave us information about the plume constitution, the temperature, the velocity of the different species of the plume and the fundamental atomic density. A calibration realized from the sum frequency signal enabled to obtain a map of the absolute number of mercury atoms in ground state. We have also demonstrated that the VUV beam handling is easier in a glove box (here filled with argon) than in vacuum. A 100 micrometer periodic pattern has been realized by lithography with PMMA and first steps towards interferometric lithography have been achieved
Saucourt, Jérémy. "Nouveau procédé dynamique d’analyse et de contrôle du front d’onde synthétique de réseaux de lasers." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0050.
Futuristic projects such as nuclear fusion power generation, or interstellar navigation by solar sails, require the use of a light source of extreme brightness. In order to increase the brightness of laser sources, my thesis work focused on the coherent beam combination of laser arrays. They led to the development of a new compact control process for the synthetic wavefront formed by the laser beam array. This process makes it possible to tailor the intensity pattern of the far field and thus control the angular distribution of energy emitted by the laser beam array. The process developed uses a phase/amplitude converter module with an integrated diffuser element. A method of measuring the transfer matrix of an optical system has been developed to characterize this field converter module. At any time, the synthetic wavefront is estimated by a phase recovery loop based on an alternating projections algorithm. This approximate calculation makes it possible to gradually adjust the phase relationships of the laser beam array to the desired arbitrary phase set. The process allows the control of a synthetic wavefront in less than 10 phase corrections, almost independently of the number of laser beams to be controlled. It is resistant to environmental defects and independent of the initial phase set. I demonstrated the compactness of the system studied by analyzing and controlling a 4 cm large synthetic pupil, composed of 16 beams, using an analysis module measuring only 30 cm. I also experimentally showed the control of the network phases of 16 to 100 laser beams with residual errors of λ/30 and λ/20 rms respectively. The capabilities of this method can be extended to control the higher Zernike orders of the synthetic wavefront, or more generally to directly measure the wavefront of coherent radiation
Parmentier, François. "Corrélations Hanbury-Brown et Twiss aux temps courts de faisceaux monoélectroniques dans les conducteurs balistiques." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00556458.
Philippet, Laurent. "Amplification de l'énergie d'une source VUV cohérente à 125 nm dans une plume d'ablation de mercure." Phd thesis, Université Paris-Nord - Paris XIII, 2009. http://tel.archives-ouvertes.fr/tel-00454923.
Wei, Li-Wei. "Système laser de haute-puissance pour le projet Advanced Virgo : les amplificateurs à fibre combinés de façon cohérente." Thesis, Nice, 2015. http://www.theses.fr/2015NICE4091/document.
Virgo is a cavity-enhanced Michelson interferometer built for the direct detection of gravitational waves. The Advanced Virgo project consists of major upgrades to the Virgo gravitational wave detector for an order of magnitude improvement in differential strain sensitivity, one of which is the tenfold increase in injected laser power to 175 Watts. The use of fiber laser amplifiers and their coherent combination are foreseen to deliver the required high-power low-noise beam. In this thesis work, we review the laser requirements for gravitational wave detectors, introduce the design of the laser system for Advanced Virgo, and develop the means for laser characterization in accordance with the stringent noise specifications. We then present the results to date, notably the quasi-continuous long-term operation of two 40-Watt fiber laser amplifiers over thousands of hours and their coherent combination with Mach-Zehnder interferometry. Although the targeted power for Advanced Virgo is not yet attained, the developed system shows decent noise performance and is promising for further power-scaling efforts
de, Lamare Jacques. "Distorsions spatiales et temporelles subies par des impulsions laser en propagation cohérente dans des milieux optiquement épais." Paris 6, 1993. http://www.theses.fr/1993PA066691.
KHALFALLAH, Sabry. "Modulateurs de cohérence en optique intégrée sur semiconducteurs III.V : guide biréfringent et interféromètre de Mach-Zehnder." Phd thesis, Université Paul Sabatier - Toulouse III, 1997. http://tel.archives-ouvertes.fr/tel-00010242.
Heilmann, Anke. "Highly scalable femtosecond coherent beam combining system of high power fiber amplifiers." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX112/document.
Future applications of high power ultrafast laser systems require simultaneously high average and peak powers. A technique which has proved to be capable of meeting these demands is coherent beam combining (CBC).In this technique, the beam is spatially split prior to amplification, and coherently recombined in one single beam afterwards. In order to achieve an efficient recombination, the spatial and spectral properties of all beams need to be perfectly matched.For applications such as particle acceleration, the coherent combining of several thousands of fibers needs to be considered. It is thus necessary to investigate highly scalable CBC architectures.The XCAN project aims at a first demonstration of such a scalable setup by coherently combining 61 fiber amplifiers. In order to study the scientific and technical challenges of such a system, a downscaled version consisting of seven fibers has been implemented.The design and characterization of this prototype is the subject of this thesis.As a starting point, numerical simulations have been performed in order to estimate the maximum tolerable mismatches between the spatial and spectral properties of the beams.Based on this modeling work, a seven fiber CBC system has been assembled and characterized. The obtained results are very promising and imply that our setup is well suited for the accommodation of all 61 fibers of the final XCAN demonstrator
Griveau, Amélie. "Characterization and function of Dbx1-derived Cajal-Retzius cells during cerebral cortex development." Paris 6, 2009. http://www.theses.fr/2009PA066265.
Michaud, Julien. "Effet des déflecteurs électrostatiques et des champs de fuite associés sur la cohérence de spin pour la mesure du moment électrique dipolaire du proton sur anneau de stockage." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY031.
Particle accelerators are one of the most efficient ways to study matter andelementary particles, as proved by the recent discovery of the Higgs Bosonon the Large Hadron Collider.The JEDI collaboration propose to measurethe value of the proton electric dipole moment (EDM) with a precision of〖10〗^(-29) e.cm using a storage ring.A measurement of such a value of EDM, above the extremely small predictionof Standard Model would lead to new physics, by adding an additionalsource of CP violation. The CP violation is one of the three conditionsnecessary to explain the un-understanded asymetry between matter andantimatter in the universe.In order to achieve this 〖10〗^(-29)e.cm precision, one need to store the measuredparticles for many seconds in an electric field : a storage ring appearsas an ideal solution for charged particles. One of the main issues consistsin keeping the beam spin-coherent during the whole duration of the measurement.An excellent control of systematics and understanding of thespin dynamics to perform this measurement are mandatory.The electrostatic deflectors used in the experiment to provide both bendingand EDM-induced spin precession could lead to systematic errors andspin decoherence. The internal part of the deflectors and especially theirfringe fields need to be understand, in terms of trajectories and spin dynamics.This thesis provide models for fields, trajectories, spin dynamics and alsoresults about the spin decoherence induced by the deflectors.The first part is dedicated to the context around EDM measurements,and will then focus on the storage ring method. Also a first approach tothe spin precession equation and spin coherence time will be done, and theproblematic about the electrostatic deflectors exposed.The second part describes in details the analytic or semi-analytic modelswe developed. The first model describes the electric fringe field of thedeflector, using conformal mapping.This model takes into account boundary conditions like the vacuum chamberor a diaphragm and propose universal formulas as a function of theratio between gap and radius. The second model concerns trajectories inthe deflector and the fringe fields.It is using an Hamiltonian integration, variation of parameters and quadratureformulas to integrate the previously found field. This is done at thesecond order.The last model is about spin dynamics and allows the user to compute thespin total precession in the deflector or the fringe fields by using a list ofintegrals of the field. The final spin transfer solution is a function of theinitial conditions (x,px,y,py,dz,_P/P) at the second order.The last part shows the implementation on BMAD and the differenteffects of deflectors/fringe fields on the spin coherence time
Hertz, Edouard. "Interactions cohérentes dans les atomes et les molécules : manipulation des états du continuum et contrôle de paquets d'ondes rotationnels." Dijon, 2000. http://www.theses.fr/2000DIJOS045.
Sala, Francesco. "Some topics in the geometry of framed sheaves and their moduli spaces." Doctoral thesis, SISSA, 2011. http://hdl.handle.net/20.500.11767/4129.
Sala, Francesco. "Some topics in the geometry of framed sheaves and their moduli spaces." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10076/document.
The thesis is concerned with the study of framed sheaves on nonsingular projective varieties and the geometrical properties of their moduli spaces. In particular, it deals with a generalization to the framed case of known results for (semi)stable torsion free nonframed sheaves, such as the existence of the (relative) Harder-Narasimhan filtration, Mehta-Ramanathan restriction theorems, Uhlenbeck-Donaldson compactification, the definition of the relative Atiyah class and the description of the Kodaira-Spencer map in terms of the relative Atiyah class, the existence of a symplectic structure, in certain cases, on the moduli spaces of framed sheaves
Kabeya, David. "Montée en brillance des réseaux de lasers à fibre : Nouvelle approche par diagnostic à contraste de phase dans une boucle d’optimisation." Thesis, Limoges, 2016. http://www.theses.fr/2016LIMO0116/document.
Coherent laser beam combining techniques rapidly appeared highly promising in the field of ultra-high power laser sources. Indeed, the combined intensity around the propagation axis follows a quadratic law with the number of combined emitters. The first part of my work has been focused on passive phasing techniques, based on self-organization properties of coupled lasers. We have shown, both numerically and experimentally, that the intracavity filtering function due to the interferometric nature of the set-up, is an intrinsic reason for combining efficiency decrease far above laser threshold. The decrease goes steeper when the number of combined laser increases, making that kind of system inappropriate for coherently combining a large number of lasers delivering high power. The second part of my work consisted in studying an innovative active phasing method that associates a phase-contrast like filter with an optimization algorithm reducing phase errors between emitters. Both simulations and experiments showed the weak sensitivity of this method to the number of combined emitters. We demonstrated the phasing of 7 to 37 fiber lasers, delivering up to 5W each. To the best of our knowledge, this last result is the highest number of fiber lasers combined with an active phasing method. The combining efficiency has been estimated around 94%, corresponding to a residual phase error of λ/25. The weak number of algorithm iterations needed to reach the in-phase regime offered a bandwidth of approximately 1kHz
Poineau, Jérôme. "Espaces de Berkovich sur Z." Phd thesis, Université Rennes 1, 2007. http://tel.archives-ouvertes.fr/tel-00193626.
La majeure partie de notre travail est consacrée à la droite analytique. Elle jouit de propriétés semblables à celles des espaces analytiques complexes d'un point de vue topologique, mais également algébrique, son faisceau structural étant cohérent. En outre, en termes cohomologiques, ses disques se comportent comme des espaces de Stein.
Pour finir, nous exposons quelques applications des résultats géométriques énoncés auparavant. Nous obtenons ainsi quelques propriétés de classes de fonctions particulières, telles les fonctions holomorphes sur un disque contenu dans C et dont le développement en un point est à coefficients entiers.
Grivaux, Julien. "Quelques problèmes de géométrie complexe et presque complexe." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00460334.
Calvet, Pierre. "Mise en forme spatiale dans une fibre optique microstructurée pour la réalisation d'amplificateurs lasers tout fibrés pour les pilotes des lasers de puissance." Thesis, Lille 1, 2014. http://www.theses.fr/2014LIL10113/document.
Spatial beam shaping is an important topic for the lasers applications. For various industrial areas (marking, drilling, laser-matter interaction, high-power laser seeding…) the optical beam has to be flattened. Currently, the state of the art of the beam shaping: “free-space” solutions or highly multimode fibers, are not fully suitable. The first ones are very sensitive to any perturbations and the maintenance is challenging, the second ones cannot deliver a coherent beam. For this reason, we present in this manuscript a microstructured optical single-mode fiber delivering a spatially flattened beam. This “Top-Hat” fiber can shape any beam in a spatially coherent beam what is a progress with respect to the highly multimode fibers used in the state of the art. The optical fibers are easy to use and very robust, what is a strong benefit with respect to the “free-space” solutions. Thanks to this fiber, we could realize an all-fiber multi-stage laser chain to amplify a 10 ns pulse to 100 µJ. Moreover the temporal, spectral and spatial properties were preserved. We adapted this “Top-Hat” fiber to this multi-stage laser chain, we proved the capability and the interest of this fiber for the spatial beam shaping of the laser beams in highly performing and robust laser systems
Soulisse, Pierre. "Développement d'un dispositif expérimental pour la diffraction d'atomes rapides et étude de surfaces d'isolants ioniques." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00625450.
Usnich, Alexandr. "Sur le groupe de Cremona et ses sous-groupes." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2008. http://tel.archives-ouvertes.fr/tel-00812808.
Hakhumyan, Hrant. "Study of optical and magneto processes in Rb atomic vapor layer of nanometric thickness." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00764958.
Höring, Andreas. "Deux applications de la positivité à l'étude des variétés projectives complexes." Phd thesis, 2006. http://tel.archives-ouvertes.fr/tel-00121528.
La première question étudiée est de savoir si le revêtement universel d'une variété kählérienne lisse compacte avec un fibré tangent décomposé est un produit de deux variétés. A l'aide des familles couvrantes de courbes rationnelles nous montrons que certaines variétés avec un fibré tangent décomposé possèdent une structure d'espace fibré. Une étude systématique nous permet de donner une réponse affirmative à la question pour plusieurs classes de variétés.
La deuxième question étudiée est de savoir si la positivité d'un fibré en droites implique la positivité de l'image directe, par un morphisme projectif et plat, du fibré en droites adjoint. La réponse à cette question dépend de la positivité du fibré en droites et de ses liens avec la géométrie du morphisme considéré. Nous donnons une réponse positive à la question sous de faibles conditions géométriques.
PALI, Nefton. "Structures différentielles en géométrie complexe et presque complexe." Phd thesis, 2004. http://tel.archives-ouvertes.fr/tel-00007104.