Evaporative Cooling in a Crossed Dipole Trap

Laser cooled sodium atoms are trapped in an optical dipole force trap formed by the intersection of two 1.06 {μ}m laser beams. Densities as high as 4×10¹² atoms/cm³ at a temperature of ~140 {μ}K have been obtained in a ~900 {μ}K deep trap. By reducing the trap depth over a 2 s interval, we have evaporatively cooled the atoms to a final temperature of ~4 {μ}K at a density of 6×10¹¹ atoms/cm³. This corresponds to a factor of 28 increase in atomic phase-space density.