Laser collimation of a continuous beam of cold atoms using Zeeman-shift degenerate-Raman-sideband cooling

Abstract

In this article we report on the use of degenerate-Raman-sideband cooling for the collimation of a continuous beam of cold cesium atoms in a fountain geometry. Thanks to this powerful cooling technique we have reduced the atomic beam transverse temperature from $60\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}\phantom{\rule{0.5em}{0ex}}\text{to}\phantom{\rule{0.5em}{0ex}}1.6\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ in a few milliseconds. The longitudinal temperature of $80\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{K}$ is not modified. The flux density, measured after a parabolic flight of $0.57\phantom{\rule{0.3em}{0ex}}\mathrm{s}$, has been increased by a factor of 4 to approximately ${10}^{7}\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}\phantom{\rule{0.2em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}2}$ and we have identified a Sisyphus-like precooling mechanism which should make it possible to increase this flux density by an order of magnitude.