Time dependence of laser cooling in optical lattices

C. M. Dion, P. Sjölund, S. J. H. Petra, S. Jonsell, and A. Kastberg

Department of Physics, Umeå University, SE-901 87 Umeå, Sweden

We study the dynamics of the cooling of a gas of caesium atoms in an optical lattice, both experimentally and with full-quantum Monte Carlo simulations. We find that, contrary to the standard interpretation of the Sisyphus model, the cooling process does not work by a continuous decrease of the average kinetic energy of the atoms in the lattice. Instead, we show that the momentum of the atoms follows a bimodal distribution, the atoms being gradually transferred from a hot to a cold mode. We suggest that the cooling mechanism should be depicted in terms of a rate model, describing the transfer between the two modes along with the processes occurring within each mode.

This article has been published in Europhysics Letters 72, 369 (2005).

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