Optical Conveyor-Belt Transport of Cs and Rb Atoms

Abstract

In this thesis the fast and efficient transport of Caesium and Rubidium atoms using an optical conveyor-belt is presented. Up to atoms of either species can be transported in under ms across the cm gap between the MOT Chamber, where they are initially cooled, and the Science Cell, where future experiments will be performed. Once in the Science Cell, either species can be evaporatively cooled to form a Bose-Einstein condensate. Simultaneously loading both species into the optical-conveyor belt did not lead to a reduction in the transport efficiency of either species.

Our transport scheme was able to avoid the use of more complicated Bessel beams or variable-focus lenses by carefully choosing the waists and focus positions. To that end detailed calculations of the trapping potential were performed to find the optimum beam parameters. It was found that separating the focus positions of the two transport beams can lead to dramatic increases in the minimum trap depth. The use of magnetic coils at the start and end of the transport path, to compensate for the effect of gravity, was also found to be highly beneficial. Beam waists of m and focus positions cm from each end of the transport paths were found to be optimum for both species.

The setup and implementation of the two transport beams is presented and the performance of the transport characterised. The equations of motions of several different transport trajectories are derived and compared both theoretically and experimentally. The performance of the Minimum Jerk Trajectory was found to be the best, with that of the Minimum Snap Trajectory a close second. The characterisation measurements allow insight to be gained into different loss mechanism during transport.