Loading an optical dipole trap
We present a detailed experimental study of the physics involved in transferring atoms from a magneto-optical 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 atoms into the trapping volume, and the loss rate is due to excited slate collisions induced by the MOT light fields. From this study we found ways to optimize the loading of the optical dipole trap. Key ingredients, for maximum loading are found to be a reduction of the hyperfine repump intensity, increased detuning of the MOT light, and a displacement or the optical dipole trap center with respect to the MOT. A factor of 2 increase in the number of loaded atoms is demonstrated by using a hyperfine repump beam with a shadow n it. In this way we load 8 × 106 85Rb atoms into a 1 mK deep optical dipole trap with a worst of 58 μm, which is 40% of the atoms initially trapped in the MOT.
