Three-dimensional cooling of cesium atoms in four-beam gray optical molasses

We report the observation of three-dimensional cooling of cesium atoms using a four-beam optical molasses tuned to the blue side of the ${\mathit{F}}_{\mathit{g}}$=3→${\mathit{F}}_{\mathit{e}}$=2 hyperfine component of the 6${\mathit{S}}_{1/2}$→6${\mathit{P}}_{3/2}$ transition. The cooling mechanism is a Sisyphus effect involving atomic states that are nearly uncoupled from the light field. Starting from a magneto-optical trap at 70 μK, the cooling time was on the order of 1 ms with almost 100% capture efficiency and temperature smaller than 5 μK measured. We also present a probe transmission spectrum showing that almost all the atoms are found in the nearly dark states.