Loading an optical dipole trap - art. no. 013406

We present a detailed experimental study of the physics involved in transfe rring atoms from a magnetooptical trap (MOT) to an optical dipole trap. The loading is a dynamical process determined by a loading rate and a density dependent loss rate. The loading rate depends on cooling and the flux of at oms into the trapping volume, and the loss rate is due to excited state col lisions induced by the MOT light fields. From this study we found ways to o ptimize the loading of the optical dipole trap. Key ingredients for maximum loading are found to be a reduction of the hyperfine repump intensity, inc reased detuning of the MOT light, and a displacement of the optical dipole trap center with respect to the MOT. A factor of 2 increase in the number o f loaded atoms is demonstrated by using a hyperfine repump beam with a shad ow in it. In this way we load 8 X 10(6) Rb-85 atoms into a 1 mK deep optica l dipole trap with a waist of 58 mu m, which is 40% of the atoms initially trapped in the MOT.