关键词: 二维磁光阱/
四极磁阱/
马约拉纳损耗/
玻色-爱因斯坦凝聚体
English Abstract
Fast production of 87Rb Bose-Einstein condensates
Chen Liang-Chao1,2,Meng Zeng-Ming1,2,
Wang Peng-Jun1,2
1.State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China;
2.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. 2016YFA0301602), the National Natural Science Foundation of China (Grant Nos. 11234008, 11361161002, 11474188), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011008.2).Received Date:26 October 2016
Accepted Date:12 February 2017
Published Online:05 April 2017
Abstract:A rapid atomic beam of rubidium (87Rb) is produced by two-dimensional magneto-optical trap (2D MOT), and then trapped by three-dimensional magneto-optical trap (3D MOT) with high vacuum for further cooling. After a process of optical molasses cooling, atoms are reloaded into a magnetic trap, where radio frequency (RF) evaporation cooling is implemented. The precooled atoms in the magnetic trap are then transferred into a far detuning optical dipole trap, where Bose-Einstein condensate (BEC) appears by further evaporation cooling. The 3D MOT is loaded to its maximum within 25 s and then BEC is prepared in 16 s. Due to the linear intensity of magnetic trap, the frequency can be scanned fast in the RF evaporation cooling process. In our experiment, the frequency scans from 39 MHz to 15 MHz in 6 s and then scans to 2 MHz in 5 s. The number of atoms in 3D MOT is about 11010, and there are 5105 atoms in the BEC after a succession of cooling processes. To optimize the performances of 2D MOT, a special light path is constructed. And prisms with high reflectivity are used to reduce the imbalance between opposite propagating cooling +beams. Furthermore, quarter-wave plates are used to keep the polarization state of the cooling beam when reflected by prisms or mirrors. The atoms are cooled to a temperature about 15 K in the magnetic trap by RF evaporation. In such a low temperature, the loss of magnetic trap (Majorana loss) will prevent the atoms from reaching a high density, and the atoms cannot be cooled further. To reduce the loss rate of the magnetic trap, the far blue detuning light (532 nm, 18 W) is added to plug the zero point of the magnetic trap. In the optically plugged magnetic trap, atoms with high density are cooled down enough, which gives a good start for the loading of optical dipole trap.
Keywords: two-dimensional magneto-optical trap/
quadruple magnetic trap/
Majorana loss/
Bose-Einstein condensates
