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

TL;DR

This paper demonstrates efficient sub-Doppler gray molasses cooling of sodium atoms on the D2 line, significantly reducing temperature and improving loading efficiency into magnetic traps, with potential for fast sodium atom cooling.

Contribution

It introduces a novel gray molasses cooling method on the D2 line for sodium, achieving rapid cooling from 700 μK to 56 μK and enhancing trap loading efficiency.

Findings

Temperature reduced from 700 μK to 56 μK

Cooling duration of 3.5 ms

Increased magnetic trap loading efficiency

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 $|F'=2\rangle$ and $|F'=3\rangle$ 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.