Contrôle des micro-ondes en milieux réverbérants

Abstract : This thesis, dealing with controlling microwaves in reverberating media, is in the straight line of previous works performed at the Institut Langevin. We start by considering the general principles of the propagation of waves in complex media, which are basically reverberating or multiple scattering media. We review the concept of degrees of freedom and explain why techniques such as time reversai and wave front shaping are efficient to control waves in such media. We introduce a novel and efficient way to control the coupling of a cavity to the exterior. To do so, we propose to open a cavity with a sub-wavelength diffraction grating. We show that the latter behaves as a partially reflecting mirror. We then show how we can replace such grating by a fractal planar resonator in order to focus waves on very subwavelength dimensions Finally we detail the concept, the design and the use of a reconfigurable reflect array that allow to passively control spatial degrees of freedom of a reverberating media. We show that this modulator permits to optimize a signal at WIFI frequencies by shaping the field in a similar way than it is done in scattering media in otpics with spatial light modulators. We present a mode) adapted to our situation and a new numerical approach based on the boundary layers potential to obtain the eigenmodes of a cavity with mixed boundary conditions.
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  • HAL Id : tel-01325120, version 1

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Matthieu Dupré. Contrôle des micro-ondes en milieux réverbérants. Optique [physics.optics]. Université Paris 7, 2015. Français. ⟨tel-01325120⟩

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