Deeply subrecoil two-dimensional Raman cooling

Abstract

We report the implementation of a two-dimensional Raman cooling scheme using sequential excitations along the orthogonal axes. Using square pulses, we have cooled a cloud of ultracold cesium atoms down to an rms velocity spread of 0.39(5) recoil velocities, corresponding to an effective transverse temperature of $30\phantom{\rule{0.3em}{0ex}}\mathrm{nK}$ $(0.15{T}_{\mathrm{rec}})$. This technique can be useful to improve cold-atom atomic clocks and is particularly relevant for clocks in microgravity.