关键词: 磁悬浮/
拉曼边带冷却/
Dimple光学偶极阱
English Abstract
Inverstigation on loading of the Dimple optical trap based on a magnetically levitated large-volume crossed optical dipole trap
Wang Xiao-Feng,Li Yu-Qing,
Feng Guo-Sheng,
Wu Ji-Zhou,
Ma Jie,
Xiao Lian-Tuan,
Jia Suo-Tang
1.State Key Laboratory of Quantum Optics and Quantum Optic Devices, Institute of Laser Spectroscopy, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Fund Project:Project supported by the National Basic Research Program of China (Grant No. 2012CB921603), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT13076), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91436108), the National Natural Science Foundation of China (Grant Nos. 61378014, 61308023, 61378015, 11434007), the New Teacher Fund of the Ministry of Education of China (Grant No. 20131401120012), and the Natural Science Foundation for Young Scientists of Shanxi Province, China (Grant No. 2013021005-1).Received Date:24 December 2015
Accepted Date:25 January 2016
Published Online:05 April 2016
Abstract:Optical trapping techniques and the ability to tune the atomic interactions both have made the unprecedented progress in the quantum gas research field. The major advantage of the optical trap is that the atoms are likely to be trapped at various sub-levels of the electronic ground state and the interaction strength can be controlled by Feshbach resonance. Optical trapping methods in combination with magnetic tuning of the scattering properties directly lead to the experimental achievements of Bose-Einstein condensation (BEC) of Cesium, which at first failed by using magnetic trapping approaches due to the large inelastic collision rate. The rapid loss of cesium atoms due to the inelastic two-body collisions greatly suppresses the efficient evaporative cooling to obtain a condensate.For optical production of cesium atomic BEC, it is necessary to prepare a large number of Cs atoms at specified state in an optical trap for condensation, especially for an efficient forced evaporation cooling. In this paper, we demonstrate our research on enhancing the loading rate of the atoms by using a dimple trap combined with a large-volume optical dipole trap (reservoir trap). In our work, the cold cesium atoms are prepared by a three-dimensional degenerated Raman sideband cooling, and then loaded into a large-volume crossed dipole trap by using the magnetic levitation technique. Effective load of the dimple optical trap is realized by superposing the small-volume dimple trap on the center of the largevolume optical trap. The theoretical analyses are performed for the magnetically levitated large-volume crossed dipole trap in variable magnetic field gradients and uniform bias fields. Optimal experimental values are acquired accordingly. The combined potential curve of the dimple trap, which is superimposed on the magnetically levitated large-volume dipole trap, is also given. The loading of precooled atoms from Raman sideband cooling into the magnetically levitated large-volume optical trap is measured in variable magnetic field gradients and uniform bias fields. Different loading results of the dimple trap are investigated, including direct loading after Raman sideband cooling, the large-volume optical trap and the magnetically levitated large-volume dipole trap without anti-trapping potential. Comparatively, the atomic number density is enhanced by a factor of ~15 by loading the atomic sample from the magnetically levitated large-volume dipole trap into the dimple optical trap. The experimental results lay a sound basis for the further cooling and densifying the atomic cloud through the evaporating cooling stage. This method can be used to obtain more cold atoms or a large number of Bose-Einstein condensation atoms for atomic species with large atom mass.
Keywords: magnetic levitation/
Raman sideband cooling/
Dimple optical trap
