Enhanced optical molasses cooling for Cs atoms with largely detuned cooling lasers

We report a detailed study of the enhanced optical molasses cooling of Cs atoms, whose large hyperfine structure allows to use the largely red-detuned cooling lasers. We find that the combination of a large frequency detuning of about -110 MHz for the cooling laser and a suitable control for the powers of the cooling and repumping lasers allows to reach a cold temperature of ~5.5 μK. We obtain 5.1×10⁷ atoms with the number density around 1×10¹² cm^-3. Our result gains a lower temperature than that got in other experiments, in which the cold Cs atoms with the temperature of ~10 μK have been achieved by the optical molasses cooling.