Sub-Doppler laser cooling of 23Na in gray molasses on the D2 line

Abstract

We report on the efficient gray molasses cooling of sodium atoms using the $D_2$ optical transition at 589.1 nm. Thanks to the hyperfine split about 6$\Gamma$ between the $|F^{\prime }=2⟩$ and $|F^{\prime }=3⟩$ in the excited state 3${}^2{P}_{3/2}$, this atomic transition is effective for the gray molasses cooling mechanism. Using this cooling technique, the atomic sample in $F=2$ ground manifold is cooled from 700 $\upmu$K to 56 $\upmu$K in 3.5 ms. We observe that the loading efficiency into magnetic trap is increased due to the lower temperature and high phase space density of atomic cloud after gray molasses. This technique offers a promising route for the fast cooling of the sodium atoms in the $F=2$ state.

5 pages, 4 figures