Gray-molasses cooling of 39K to a high phase-space density

We present new techniques in cooling K-39 atoms using laser light close to the D1 transition. First, a new compressed-MOT configuration is taking advantage of gray-molasses-type cooling induced by blue-detuned D1 light. It yields an optimized density of atoms. Then, we use pure D1 gray molasses to further cool the atoms to an ultra-low temperature of 6 mu K. The resulting phase-space density is 2 x 10(-4) and will ease future experiments with ultracold potassium. As an example, we use it to directly load up to 3 x 10(7) atoms in a far detuned optical trap, a result that opens the way to the all-optical production of potassium degenerate gases. Copyright (C) EPLA, 2013