Дисертації з теми "Linear wave scattering"
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Jeyakumaran, R. "Some scattering and sloshing problems in linear water wave theory." Thesis, Brunel University, 1993. http://bura.brunel.ac.uk/handle/2438/5390.
Повний текст джерелаKent, William J. "Plane wave scattering by thin linear dielectric-coated wires and dielectric strips : a moment method approach with physical basis functions /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726053195675.
Повний текст джерелаGaw, Stephen Michael. "Cooperative spin excitations in quantum materials studied by neutron spectroscopy." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:c20676e1-b927-4ee5-a3fe-97f0f80cb141.
Повний текст джерелаLehner, Thierry. "Interaction quadratique onde-onde en plasma : battement d'ondes, couplage onde-fluctuations." Paris 6, 1987. http://www.theses.fr/1987PA066482.
Повний текст джерелаPham, Truong Xuan. "Peeling et scattering conforme dans les espaces-temps de la relativité générale." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0034/document.
Повний текст джерелаThis work explores two aspects of asymptotic analysis in general relativity: peeling and conformal scattering.On the one hand, the peeling is constructed for linear and nonlinear scalar fields as well as Dirac fields on Kerr spacetime, which is non-stationary and merely axially symmetric. This generalizes the work of L. Mason and J-P. Nicolas (2009, 2012). The vector field method (geometric energy estimates) and the conformal technique are developed. They allow us to formulate the definition of the peeling at all orders and to obtain the optimal space of initial data which guarantees these behaviours. On the other hand, a conformal scattering theory for the spin-n/2 zero rest-mass equations on Minkowski spacetime is constructed. Using the conformal compactifications (full and partial), the spacetime is completed with two null hypersurfaces representing respectively the past and future end points of null geodesics. The asymptotic behaviour of fields is then obtained by solving the Cauchy problem for the rescaled equation and considering the traces of the solutions on these hypersurfaces. The invertibility of the trace operators, that to the initial data associate the future or past asymptotic behaviours, is obtained by solving the Goursat problem on the conformal boundary. The conformal scattering operator is then obtained by composing the future trace operator with the inverse of the past trace operator
Watson, Francis Maurice. "Better imaging for landmine detection : an exploration of 3D full-wave inversion for ground-penetrating radar." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/better-imaging-for-landmine-detection-an-exploration-of-3d-fullwave-inversion-for-groundpenetrating-radar(720bab5f-03a7-4531-9a56-7121609b3ef0).html.
Повний текст джерелаLafontaine, David. "Effets dispersifs et asymptotique en temps long d'équations d'ondes dans des domaines extérieurs." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4067/document.
Повний текст джерелаWe are concerned with Schrödinger and wave equations, both linear and non linear, in exterior domains. In particular, we are interested in the so-called Strichartz estimates, which are a family of dispersive estimates measuring decay for the linear flow. They turn out to be particularly useful in order to study the corresponding non linear equations. In non-captive geometries, where all the rays of geometrical optics go to infinity, many results show that Strichartz estimates hold with no loss with respect to the flat case. Moreover, the local smoothing estimates for the Schrödinger equation, respectively the local energy decay for the wave equation, which are another family of dispersive estimates, are known to fail in any captive geometry. In contrast, we show Strichartz estimates without loss in an unstable captive geometry: the exterior of many strictly convex obstacles verifying Ikawa's condition. The second part of this thesis is dedicated to the study of the long time asymptotics of the corresponding non linear equations. We expect that they behave linearly in large times, or scatter, when the domain they live in does not induce too much concentration effect. We show such a result for the non linear critical wave equation in the exterior of a class of obstacles generalizing star-shaped bodies. In the exterior of two strictly convex obstacles, we obtain a rigidity result concerning compact flow solutions, which is a first step toward a general result. Finally, we consider the non linear Schrödinger equation in the free space but with a potential. We prove that solutions scatter for a repulsive potential, and for a sum of two repulsive potentials with strictly convex level surfaces. This provides a scattering result in a framework similar to the exterior of two strictly convex obstacles
Boyle, Jonathan William. "Observation of linear and nonlinear magnetostatic waves by Brillouin light scattering." Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262623.
Повний текст джерелаMarconi, Jorge Diego. "Estudo de amplificadores paramétricos para sistemas de comunicações ópticas de altas taxas de transmissão." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277933.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Esta tese apresenta um estudo teórico e experimental sobre Amplificadores Paramétricos a Fibra Óptica. Mostramos primeiramente a potencialidade do amplificador em termos de largura de banda plana, necessária para aplicações em sistemas WDM. Foram desenvolvidas equações do ripple para os diferentes tipos de espectro de alto ganho possíveis. Usando fibras de dispersão deslocada e fibras altamente não-lineares curtas, construímos amplificadores de dois bombeios com uma banda plana de amplificação de 52 nm e 84 nm, respectivamente. Em ambos os casos, a banda obtida foi comparável à obtida com outras tecnologias como Érbio ou Raman. Pesquisamos também o crosstalk entre canais em amplificadores paramétricos. Mostramos como as variações de ë 0 ao longo da fibra aumentam o crosstalk, pois se incrementam os processos de mistura de quatro ondas espúrios. Em amplificadores de dois bombeios, obtivemos os melhores resultados para aplicações WDM com fibras curtas (L ~ 0.8 km). Finalmente, a partir da análise da penalidade do fator de mérito Q do sinal, estudamos como os efeitos da modulação de fase do/s laser/s de bombeio, necessária para suprimir o espalhamento Brillouin estimulado, são prejudiciais para a performance destes amplificadores. Com base nesse resultado, procuramos eliminar o espalhamento Brillouin com um método alternativo que consiste na aplicação de distribuições de deformação mecânica ao longo da fibra. Obtivemos um aumento de 10.7 dB em 285 m de fibra altamente não-linear, o que é da ordem dos valores obtidos modulando a fase do/s bombeio/s. Aplicamos a técnica em dispositivos paramétricos obtendo um conversor de comprimento de onda com um sinal convertido de largura de banda estreito, sintonizável ao longo de 70 nm de comprimento de onda do sinal de entrada
Abstract: This thesis presents a theoretical and experimental study on fiber optics parametric amplifiers. For the double-pumped case, we show the performance of the amplifier in terms of spectral bandwidth and gain uniformity, both fundamental properties for WDM applications. By using short dispersion shifted fibers and highly non-linear fibers, we made parametric amplifiers with 52 and 84 nm of flat bandwidth, respectively. In both cases, the bandwidth is similar to the one obtained with optical amplifiers based on other technologies such as doped fibers, Raman gain or semiconductors. We also deduced equations of the gain ripple for all the possible types of high gain spectra. We also investigated the inter-channel crosstalk in parametric amplifiers. We showed that the variations of the zero dispersion wavelength along the fiber increase the crosstalk because those variations enhances the spurious four wave mixing tones. Finally, the degradation of the signal quality factor (Q) was studied for both, single and double-pumped parametric amplifiers. We showed that the phase modulation applied to the pump lasers to suppress the stimulated Brillouin backscattering can strongly degrade the performance of the amplifier. One alternative technique that we developed was based on applying different mechanical stress distributions along the fiber length. We experimentally demonstrated, using 285 m of highly non-linear fibers, that the backscattering threshold can be increased by 10.7 dB. This value is similar to that obtained using the phase modulation schema. The method was successfully applied to parametric devices. In particular we made a narrow linewidth wavelength converter with 70 nm of signal tuning band
Doutorado
Física
Doutor em Ciências
Ferrier, Jean-Louis. "Contribution à l'étude de la conjugaison de phase, en régime d'excitation picoseconde, dans les milieux liquides et cristallins : faisabilité, caractérisation et applications." Angers, 1986. http://www.theses.fr/1986ANGE0003.
Повний текст джерелаTomasini, Franco. "Contribution a l'etude des non-linearites optiques de chlorure de cuivre." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13111.
Повний текст джерелаPORTELLA, MARCIA TEREZA. "Spectroscopie coherente et etude d'un espace poreux par melange a quatre ondes." Paris 6, 1987. http://www.theses.fr/1987PA066586.
Повний текст джерелаDiallo, Souleymane. "Utilisation des non-linéarités Kerr et Brillouin dans les résonateurs à mode de galerie cristallins pour la synthèse de micro-ondes." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2028/document.
Повний текст джерелаWhispering galery mode resonators are dielectric cavities that support modes with ultra-high quality factor and small volume that remain confined in their inner periphery for time duratioons that can be as long as few microseconds. The strong confinement of these modes for such long durations strongly enhances nonlinear effect suchs as Kerr effect or Brillouin effect. These resonators can therefore be used for several applications such as spectroscopy, telecommunications or microwave generation. The objective of this thesis is to use Kerr and Brillouin nonlinearities in these resonators at the laser wavelength of 1550 nm, in order to generate high spectral purity microwave signals with frequencies rangong fros 5 to 30 GHz. The first chapter oh the thesis intriduces the theory, fabrication, coupling and characterisation of whispering gallery mode resonators. The second chapter is about the generation of Kerr optical frequency combs in these resonators and their application to the generation of microwave signals. We present our experimental resuktsdn the numerical modelling of Kerr combs, the analysis of oscillatory instabilities (due to thermal effect) observed during our experiments, and conclue. The third chapter concerns photon-phonon interactions via stimulated Brillouin scattering in these resonators and their application to the generation of microwave signals. We present our experimental results and the temporal model that we developed to track the dynamics of the forward and backscattered fields. The last chapter conclude the thesis. The research presented in this thesis has benne funded by the European Research Council through the project Nextphase
Svetogorova, Elena. "Integral equation approach to reflection and transmission of a plane TE-wave at a (linear/nonlinear) dielectric film with spatially varying permittivity." Doctoral thesis, 2004. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2004110212.
Повний текст джерелаWang, Hsuan-Yu, and 王暄淯. "Scattering and localization of linear and nonlinear waves in one-dimensional disordered lattices." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/95556434967219730500.
Повний текст джерела國立清華大學
光電工程研究所
101
There have been numerical investigations for electron and electromagnetic waves in the one-dimensional disordered lattice. The electron eigenmodes of one-dimensional disordered lattice are investigated for three different models. The electromagnetic eigenmodes of one-dimensional disordered lattice are also investigated. The degree of localization of the wavelength at the band, gap edge and gap are studied. Finally, the disordered lattice solitons are presented.