Search results for "polarisation"
showing 10 items of 44 documents
Sur le rôle des singularités hamiltoniennes dans les systèmes contrôlés : applications en mécanique quantique et en optique non-linéaire.
2012
This thesis has two goals: the first one is to improve the control techniques in quantum mechanics, and more specifically in NMR, by using the tools of geometric optimal control. The second one is the study of the influence of Hamiltonian singularities in controlled systems. The chapter about optimal control study three classical problems of NMR : the inversion problem, the influence of the radiation damping term, and the steady state technique. Then, we apply the geometric optimal control to the problem of the population transfert in a three levels quantum system to recover the STIRAP scheme.The two next chapters study Hamiltonian singularities. We show that they allow to control the polar…
AMPLIFICATION ET CONTROLE TOUT-OPTIQUE DE LA POLARISATION D'UN SIGNAL TELECOM CADENCE A 10 GB/S AU SEIN D'UNE FIBRE OPTIQUE
2012
National audience; Nous démontrons la possibilité de combiner l'amplification Raman et l'attraction de polarisation d'un signal retour-à-zéro cadencé à 10 Gb/s au moyen d'une onde pompe laser contra-propagative dans un unique segment de fibre
Cross-phase modulation effects in normal dispersive fibers and their applications
2018
In this Ph.D., physical effects arising from cross-phase modulation between twoorthogonally polarized signals propagating in normal dispersion fibers arestudied and some of their applications investigated.First, a 40-GHz pulse generator is designed by sending two orthogonallypolarized out-of-phase sinusoidal waves in a normally dispersive optical fiber.A large power imbalance between the two waves induces a periodic phasepotential for the weak replica which turns the normal dispersive defocusingregime into a focusing dynamics, thus compressing the sinusoidal wave intoshort and well-separated pulses.A signal sampler and magnifier was then designed using the same principle,sending a high powe…
Différents régimes impulsionnels dans un laser Raman à fibre optique
2008
National audience; Nous rapportons différents régimes impulsionnels observés au sein d'une cavité laser Raman en anneau.
Complex rogue wave in the fiber optics
2016
This manuscript presents the generation of complex rogue waves related to nonlinear instabilities occurring through the propagation of light in standard optical fibers. Linear and nonlinear physical phenomena involved are first listed, in particular some of them by analogy with the field of hydrodynamics. The different forms of rogue waves induced by the modulation instability process are then presented. They are also known as "breathers", and they are obtained by solving the nonlinear Schrödinger equation. From these exact solutions, various experimental systems were designed by means of numerical simulations based on two rogue-wave excitation methods. The first one is an exact generation …
Nouveaux systèmes de contrôle de la polarisation de la lumière par effets non lineaires dans les fibres optiques
2013
This thesis deals with the work the development of an all-optical device for the control of the polarization state of light. Actually, this feature of light remains so far an uncontrolled variable, which can degrade the performances of all-optical systems. Based on nonlinear interaction between two counterpropagating waves inside an optical fiber, this device called polarization attractor allows to control the polarization state of light without polarization dependent losses.In a first part, we carry out extensive studies of the polarization attractor properties leading to the control and the regeneration of the polarization state of the 10-Gb/s NRZ and RZ telecommunication signals. Then, t…
Frontières des communautés polarisées : application à l'étude des théories complotistes autour des vaccins
2021
Les données des réseaux sociaux sont de plus en plus utilisées pour en extraire de la valeur, dans des domaines tels que le marketing, la politique ou la sociologie. Celles-ci peuvent être représentées sous forme de graphes, en modélisant précisément les interactions à travers des liens dirigés et pondérés. Dans l'analyse des données des réseaux sociaux, l'étude des communautés est une étape essentielle. Toutefois, pour une interprétation fine des phénomènes, il est également nécessaire d'étudier leurs interactions et de pouvoir détecter des traces de polarisation. Nous proposons une méthode qui permet d'évaluer l'antagonisme des communautés et d'identifier leurs frontières dans des réseaux…
Mutations urbaines et logiques de localisation des emplois: le cas de la Communauté de l'agglomération dijonnaise (1990, 1999).
2004
The aim of this paper is to analyze the spatial changes in the Dijon urban area (COMADI) by studying in particular the new tendencies of localization of the high order producer services. Our results display a multicentric structure of the COMADI which exhibits several employment poles. Not only the economic composition of these poles differs between the central pole and the peripheral ones but this composition changes over the study period (1990-1999). New localization logics appear for the high order services : if the historical center remains specialized in financial activities, insurance and real estate (FIRE), the other producer services are more likely to be localized in the periphery.…
Measurement of top-quark polarisation observables and a search for dark matter in single-top-quark production with the ATLAS detector at the LHC
2022
Esta tesis presenta dos análisis diferentes basados en los datos resultantes de colisiones protón-protón a una energía en el centro de masas de 13 TeV recolectados con el detector ATLAS del LHC, correspondientes a una luminosidad integrada de 139 fb$^{-1}$. El primer análisis presenta una medida de secciones eficaces diferenciales normalizadas del canal de producción de quarks top en solitario $t$-channel, donde el quark top se desintegra leptónicamente, como función de los tres ángulos de polarización del leptón para eventos con quarks top y quarks antitop tanto separadamente como de forma inclusiva. Estos observables son particularmente sensibles a efectos de nueva física en el vértice $t…
Disparités géographiques et convergence des régions européennes : une approche par l'économétrie spatiale
2002
The aim of this dissertation is to analyze the convergence process between European regions by taking into account spatial patterns of economic activities. First, with the help of literature reviews on theoretical and empirical analyses of growth and convergence and on economic geography models, we show in chapter 1 why geographic disparities should be introduced in the study of convergence between economies. Next, the spatial statistic and econometric tools allowing to reach this goal are detailed in chapter 2. Finally, three empirical studies of the convergence process in presence of geographic disparities are carried out. They are based on a sample for per capita GDP of 138 regions, belo…