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Génération et détection par couplage élasto-optique tridimensionnel de champs acoustiques picosecondes diffractés

Abstract : The absorption of a laser pulse creates a localized heating, followed by a sudden dilatation. Thereby, an acoustic field of several tens of gigahertz can be launched. This optical method is applied to microelectronics to characterise nanometric films non-destructively and without contact, but also to more fondamental fields. Until now, the lateral size of the laser spot was very large compared to the films thicknesses. Thus, generation was one-dimensional, and only acoustic plane waves could be engendered. Recently, the use of focused laser sources has allowed the generation of three-dimensional (3D) diffracted acoustic fields.

When pulses shorter than a picosecond are absorbed in metals, a macroscopic approach is not relevant anymore. It is then necessary to describe the microscopic evolutions implied in the generation process. Thus, a semi-analytical method based on a 3D two-temperature model is developed in the first part of this thesis to describe the electronic phenomena. While propagating, the divergent acoustic field modulates the optical indices in time and space through the elasto-optic interaction. The light propagation is thereby perturbed, and its measurement allows the characterization of the acoustic propagation. In the second part of this thesis, the 3D interaction of the Gaussian laser pulse with the diffracted acoustic field is therefore modeled.
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https://tel.archives-ouvertes.fr/tel-00179637
Contributor : Thomas Dehoux <>
Submitted on : Tuesday, October 16, 2007 - 11:31:48 AM
Last modification on : Thursday, January 11, 2018 - 6:21:23 AM
Long-term archiving on: : Sunday, April 11, 2010 - 11:06:34 PM

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  • HAL Id : tel-00179637, version 1

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Thomas Dehoux. Génération et détection par couplage élasto-optique tridimensionnel de champs acoustiques picosecondes diffractés. Physique Atomique [physics.atom-ph]. Université Sciences et Technologies - Bordeaux I, 2007. Français. ⟨tel-00179637⟩

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