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Interférométrie avec des guides d'ondes optiques. Théorie et applications

Abstract : Interferometry is the technique that produces interferences from an astrophysical target between the output of several independent apertures. Interferometry with optical waveguides is one important subclass of interferometry for which the beams propagate in optical waveguides, the most popular ones being optical fibers. Optical waveguides are special optical components which are often not well understood by the astronomical community. They are often presented as a funnel for photons, where the number of injected photons are computed from the injection coupling factor. Neither the propagation inside the waveguide, nor the effect on the spatial spectrum of the input source are considered. The goal of the work presented in this document is to get deeper understanding of how single-mode filtering works. After an introductory chapter recalling why optical waveguides have been introduced into astronomical interferometry, I will present the physics of modal filtering from a theoretical point of view. A special emphasis has been be put on the normalization problem of Radiation Modes inside a guiding structure. A new mathematical approach for solving this problem has been derived which can be applied for any number multi-layered strong or weakling guiding dielectric structure. Application of the method to the round optical fiber has led to the computation of the spectral density of power and rejection of radiated modes launched be a perfect or perturbated Airy pattern. It is shown that rejection dynamics is fast at the beginning but slows with the optical path. Furthermore interference phenomena between radiation modes and the fundamental one can locally give rise to an optimum for the rejection in terms of the size to be used for flux integration in the tranversal plane of the waveguide. The second part of this work is dedicated to the study of the object image relationship of a fibered interferometer. On a rigorous mathematical basis we study how partial coherence propagates through interferometric combination of single-mode beams in ground-based multi-aperture long-baseline optical interferometers. We show actually that the measured visibility is biased due to field of view limitations.
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Submitted on : Tuesday, October 4, 2005 - 10:03:54 AM
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Pierre Mège. Interférométrie avec des guides d'ondes optiques. Théorie et applications. Astrophysique [astro-ph]. Université Joseph-Fourier - Grenoble I, 2002. Français. ⟨tel-00010162v2⟩

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