Beyond optical molasses: 3D Raman sideband cooling of atomic cesium to high phase-space density

We demonstrate a simple, general purpose method to cool neutral atoms. A sa mple containing 3 x 10(8) cesium atoms prepared in a magneto-optical trap i s cooled and simultaneously spin polarized in 10 ms at a density of 1.1 x 1 0(11) cm(-3) to a phase space density n lambda(dB)(3) = 1/500, which is alm ost 3 orders of magnitude higher than attainable in free space with optical molasses. The technique is based on 3D degenerate Raman sideband cooling i n optical lattices and remains efficient even at densities where the mean l attice site occupation is close to unity.