Laser cooling of cesium atoms in gray optical molasses down to 1.1 μK

Abstract

We have studied the behavior of cesium atoms cooled in six-beam "gray" optical molasses. Cooling occurs for a laser detuned to the blue side of the $6{S}_{\frac{1}{2}}$, $F=3\ensuremath{\rightarrow}6{P}_{\frac{3}{2}}$, ${F}^{\ensuremath{'}}=2$ transition, and a Sisyphus-type effect accumulates the atoms in states not coupled to the light. We measure a minimum temperature of 1.1\ifmmode\pm\else\textpm\fi{}0.1 \ensuremath{\mu}K at low atomic density. The typical cooling time is on the order of 1 ms. A linear dependence of the temperature versus atomic density is found with a slope of \ensuremath{\sim}0.6 \ensuremath{\mu}K/(${10}^{10}$ atoms/${\mathrm{cm}}^{3}$).