All-fiber laser system for all-optical ⁸⁷Rb Bose Einstein condensate to space application

Abstract

In the development of the Cold Atom Physics Research Rack (CAPR) on board the Chinese Space Station, the laser system plays a critical role in preparing the all-optical 87Rb Bose–Einstein condensates (BECs). An all-fiber laser system has been developed for CAPR to provide the required optical fields for atom interaction and to maintain the beam pointing in long-term operation. The laser system integrates a 780 nm fiber laser system and an all-fiber optical control module for sub-Doppler cooling, as well as an all-fiber 1064 nm laser system for evaporative cooling. The high-power, single-frequency 780 nm lasers are achieved through rare-Earth doped fiber amplification, fiber frequency-doubling, and frequency stabilization technology. The all-fiber optical control module divides the output of the 780 nm laser system into 15 channels and regulates them for cooling, trapping, and probing atoms. Moreover, the power consistency of each pair of cooling beams is ensured by three power tracking modules, which is a prerequisite for maintaining stable MOT and molasses. A high-power, compact, controlled-flexible, and highly stable l064 nm all-fiber laser system employing two-stage ytterbium-doped fiber amplifier (YDFA) technology has been designed for evaporative cooling in the optical dipole trap (ODT). Finally, an all-optical 87Rb BEC is realized with this all-fiber laser system, which provides an alternative solution for trapping and manipulating ultra-cold atoms in challenging environmental conditions.

Atomic transport dynamics in crossed optical dipole trap

“…However, the situation changes under microgravity conditions. When gravity is negligible such as in the Chinese Space Station, [27,28] the atoms in the arms of the CODT will not lose quickly even at the end of evaporative cooling (when the depth of the trap center and the arms are both shallow). The transport of atoms between arms and center has a non-negligible effect on the change of atomic density in the center of the trap and the state of the condensate in the trap.…”