Spin-polarized atoms in a circularly polarized optical dipole trap

The behavior of atoms in an optical far-off resonance trap is found to depend strongly on the trap polarization. Large loss rates occur unless the polarization is perfectly linear or perfectly circular, in which case exponential lifetimes up to 10 s are observed. Through optimization of trap loading, samples of 4×10⁶ atoms are obtained in a circularly polarized trap. Spin polarization of 98(1)% is measured. This trap should prove useful for precision measurements such as β-decay asymmetry and should make rf cooling possible in optical traps.