A Digital Frequency Source for Movement of Ultracold Atoms by Acousto-Optic Deflection

Abstract

This thesis documents the development of a frequency source based on a field programmable gate array (FPGA) and a direct digital synthesiser (DDS). The source was used to drive the two inputs of a dual-axis acousto-optic deflector (AOD), an integral component in a steerable optical tweezer unit designed for use with ultracold 87Rb and 40K. By synchronously changing the frequencies of the paired inputs to the AOD, an optical beam was able to be moved in two dimensions. The frequency source was used to trap and smoothly move samples of ultracold 87Rb over several millimetres, and by quickly toggling the inputs between multiple pairs of frequencies, multiple clouds were confined and moved in time-averaged potentials. The utility of the FPGA/DDS unit is shown, most notably by simultaneously evaporating four independent clouds through the Bose-Einstein Condensate (BEC) phase transition.