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Claude Cohen Tannoudji

Prix Nobel en 1997 pour le ralentissement et le piégeage des atomes par la lumière laser.

Ses travaux sont à la source des recherches actuelles de l'IFRAF.



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Accueil du site > Annonces - Congrès - Workshops > Conférences et Ateliers - IFRAF > Année 2010 > Conference of Professor Martin Weitz, Institut für Angewandte Physik, Universität Bonn, Germany.

Conference of Professor Martin Weitz, Institut für Angewandte Physik, Universität Bonn, Germany.

Friday, April 8, 2010, from 10:00 to 11:00 am, in l’ENS 29 rue d’Ulm, salle 236, Paris 75005

Laser Cooling by Collisional Redistribution of Radiation

Abstract

The general idea that optical radiation may cool matter was put forward by Pringsheim already in 1929. Doppler cooling of dilute atomic gases is an extremely successful application of this concept, and more recently anti-Stokes cooling in multilevel systems has been explored, culminating in the optical refrigeration of solids. Collisional redistribution of radiation is a proposed different cooling mechanism for atomic two-level systems, though experimental investigations in gases with moderate density have not reached the cooling regime.

Here I report on the experimental demonstration of laser cooling of an atomic gas based on collisional redistribution of radiation, using rubidium atoms in argon buffer gas at a pressure of 230 bar. The frequent collisions in the ultradense gas transiently shift a far red detuned laser beam into resonance, while spontaneous decay occurs close to the unperturbed atomic resonance frequency. During each excitation cycle, a kinetic energy of order of the thermal energy is extracted from the dense atomic sample. In a proof of principle experiment with a thermally non-isolated sample, we experimentally demonstrate relative cooling by 66 K. The cooled gas has a density of more than 10 orders of magnitude above the typical values in Doppler cooling experiments, and the cooling power reaches 87 mW. Future prospects of the demonstrated effect include studies of supercooling beyond the homogeneous nucleation temperature and optical chillers. In my talk, I will also describe experimental efforts directed at a Bose-Einstein condensation of polaritons in the high pressure buffer gas system.