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Theses

Refroidissement par bandes latérales d'atomes de Césium et quelques applications

Abstract : In the experiment presented in this thesis, Cesium atoms were trapped in a non-dissipative, intensity lattice produced by two Nd:YAG laser beams. Vertically, atoms are confined in independent micro-planes at each intensity maximum. The gaussian shape of the beams provides the horizontal confinement. Thanks to the strong vertical confinement, we could develop an optical sideband cooling method which accumulates about 95% of the atoms in the ground state of the vertical motion. From this state, which is almost pure, we prepared other pure quantum states and, using an absoption imaging technique, we visualized directly their velocity distribution. First, we produced the first excited state of motion whose velocity distribution is zero for v = 0. We also produced non stationary states and visualized the temporal evolution of their velocity distribution. In this way, the evolution of a superposition of the first two vibrationnal states and that of squeezed states have been recorded. Squeezed states are, as the ground state, minimum uncertainty states (ΔpΔz = \hbar /2), but their velocity distribution is narrower than that of the ground state. A compression of the velocity distribution by a factor 4 has been obtained. By applying the cooling of the vertical motion for a long time, thanks to the energy transfer from the horizontal to the vertical direction provided by the collisions, we cooled the movement in all three directions. In this way, we obtained a temperature T ~ 3 µK for which 80% of the atoms are in the ground state of the vertical movement. The gas thus realized is pratically a two-dimensionnal gas. Finally, the study of thermalization showed that the scattering resonnance at zero energy of Cesium is not affected by the strong vertical confinement.
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Submitted on : Tuesday, March 7, 2006 - 11:27:51 AM
Last modification on : Wednesday, December 9, 2020 - 3:45:52 AM
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  • HAL Id : tel-00011771, version 1

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Isabelle Bouchoule. Refroidissement par bandes latérales d'atomes de Césium et quelques applications. Physique Atomique [physics.atom-ph]. Université Pierre et Marie Curie - Paris VI, 2000. Français. ⟨tel-00011771⟩

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