Sub-recoil laser cooling with precooled atoms

This Note describes a new realization of sub-recoil laser cooling by Velocity Selective Coherent Population Trapping (VSCPT). Starting from a cloud of trapped and precooled metastable helium atoms, we have been able to increase the VSCPT interaction time by one order of magnitude over the previous experiment. The resulting temperature T is now 20 times smaller than the recoil temperature TR associated with the kinetic energy of an atom absorbing or emitting a single photon. The corresponding temperature is 200 nK and the atomic de Broglie wavelength is 4.5 μm