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Condensats de Bose-Einstein et lasers à atomes

Yann Le Coq 1
1 laboratoire Charles Fabry de l'Institut d'Optique / Optique atomique
LCFIO - Laboratoire Charles Fabry de l'Institut d'Optique
Abstract : Bose-Einstein condensates in dilute vapor obtained in magnetic traps consist of a macroscopic accumulation of atoms in the same wavefunction. Hence, they represent a matter wave analog of photons stored in a laser cavity in photonic optics. Just as in optics, we need to extract them from the cavity in a controlled way, so as to use them as a coherent source. We use a weak radio-frequency electromagnetic field to induce a coupling of the atoms to a magnetically untrapped internal state. The untrapped atoms then fall under the effect of gravity. We thus obtain a coherent and continuous matter wave until the source condensate is exhausted. We study the transverse properties of such coherent atomic beams. Specifically, we observe and measure the angular divergence of the atomic beam for different experimental parameters. A theory based on ABCD matrices, analogous to that of photon optics, gives good agreement with experimental data. We find that the dominant contribution to the divergence of the atom laser beam is due to interactions between the Bose-Einstein condensate and the atoms in the laser. This is in stark contrast to photonic lasers. Finally, we interfere different atom laser beams extracted from the same Bose-Einstein condensate. The patterns we observe are qualitatively and quantitatively well-described by a theory adapted from coherent Fourier optics theory.
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Submitted on : Wednesday, March 19, 2003 - 12:39:41 PM
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  • HAL Id : tel-00002564, version 1

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Yann Le Coq. Condensats de Bose-Einstein et lasers à atomes. Physique Atomique [physics.atom-ph]. Université Paris Sud - Paris XI, 2002. Français. ⟨tel-00002564⟩

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