Collective Laser Cooling of Trapped Atoms

We show that by a suciently slow repumping process, one can avoid the problems of reabsorptions in laser cooling of trapped atoms, even in the case of optically thick samples. 03.75Fi, 42.50.Fx,32.70.Js Typeset using REVT E X In a series of experiments, Bose{Einstein condensation (BEC) of a trapped weakly interacting gas has been observed [1,2]. The low temperatures and high densities required for BEC have been obtained thanks to the combination of evaporative, and laser cooling techniques [3]. Still, one of the goals of atomic physics is to attain BEC using laser cooling alone. In such a case the number of atoms in the trap would not decrease during the cooling process, and a non{destructive detection of BEC could be performed by simply measuring the uorescence photons. The obstacle to achieve BEC using laser cooling is reabsorption [4]. Typically [5,6], the scenario for laser cooling of trapped atoms is as follows [see Fig. 1(a)]: rst, one precools the atoms (optical molasses) in t..