Stimulated Raman transitions for cooling atoms in an optical dipole trap

Optical dipole traps can provide strong, state-independent confinement of atoms. Unfortunately, the spatially dependent light shifts of optical transitions in dipole traps can interfere with conventional laser cooling techniques. These limitations may be overcome by cooling trapped atoms with stimulated Raman transitions. In particular, the lights shifts of ground state sublevels can be equal, so that the Raman cooling transition is unperturbed. Cooling in the sideband limit, to the quantum ground state of motion, should be possible. We have confined {sup 85}Rb atoms in a far-detuned optical dipole trap, and indirectly measured extremely low heating rates of the trapped atoms. We have also driven velocity-sensitive stimulated Raman transitions of the trapped atoms. The high resolution of these stimulated Raman resonances should allow us to resolve the motional sidebands and to directly cool the trapped atoms.