A Proposal for Optically Cooling Atoms to Temperature of 10⁻⁶ K

Abstract

We propose an optical method for the three-dimensional cooling of collections of atoms to extremely low temperatures. With this method it should be possible to cool sodium atoms to temperatures of 10⁻⁶K or less. These low temperatures correspond to velocities less than the recoil velocity of an atom emitting a single resonant photon. Although the method is straightforward in principle, it anticipates the demonstration of optical traps capable of localizing (trapping) atoms within small regions of space (dimensions on the order of 1–100μm) and of cooling them to temperatures on the order of the “quantum limit” kT=hγ/2, where γ is the natural linewidth of the resonant transition. The recent laser cooling of sodium atoms to the “quantum limit” of 2.4 ×10⁻⁴k [1] suggest that this prerequisite will be met in the near future. Several schemes have been proposed previously for the cooling of magnetically trapped atoms to temperatures below hγ/2.[2], [3]. The magnetic trapping of sodium atoms [4] opens up the possibility for trying those schemes.