全光学冷却与囚禁^(133)Cs原子玻色-爱因斯坦凝聚的可能性

POSSIBILITY OF ALL OPTICALLY-COOLED AND TRAPPED ^(133)Cs ATOMIC BEC

综述了近年来有关蒸发冷却13 3 Cs原子样品的实验进展 ,分析了磁囚禁13 3 Cs原子玻色 爱因斯坦凝聚 (BEC)的困难 ,并在此基础上提出了一个全光型冷却与囚禁13 3 Cs原子BEC的新方案 .该方案主要由一个来自半导体激光 (λ=0 85 2 μm)的倒金字塔形中空光束重力光学囚禁 (pyramidal hollow beam gravito opticaltrap ,缩写为PHBGOT)和一个来自Ar+ 激光 ( λ =0 5 0 13μm)的圆锥形中空光束重力光学囚禁 (conical hollow beam gravito opticaltrap ,缩写为CHBGOT)组成 .在PHBGOT中 ,冷原子经历了一个有效的中空光束感应的Sisyphus冷却 (也即强度梯度冷却 )和抽运光感应的几何冷却 ,原子温度将被从磁光囚禁 (MOT)温度 (约为 6 0 μK)冷却至几个光子反冲极限 (约为2 μK) ;而在Ar+ 中空光束囚禁 (CHBGOT)中 ,冷原子将被Raman冷却或速度选择相干粒子数囚禁技术 (velocity se lectioncoherentpopulationtrap ,缩写为VSCPT)进一步冷却至光子反冲极限以下 ,并被激光频率高于原子共振频率的 (也即蓝失谐的 )covering光束压缩 .我们就PHB冷却的动力学过程进行了Monte Carlo模拟 ,并计算了Ar+ 中空光束囚禁13 3 Cs原子的光学势 .研究结果表明 ,实现一个全光学冷却与囚禁的13 3

The experimental progress on rf evaporative cooling of 133 Cs atomic sample in recent year is reviewed, and the difficulty of magnetically trapped 133 Cs atomic Bose Einstein condensation (BEC) is analyzed. In this paper, we propose an all optically cooled and trapped 133 Cs BEC scheme, which is composed of a pyramidal hollow beam gravito optical trap (PHB GOT) from a diode laser ( λ =0.852 μm) and a conical hollow beam (CHB) GOT from an Ar + laser ( =0.5013 μm). In the PHB GOT, the cold atoms experience an efficient hollow beam induced Sisyphus cooling (i.e., intensity gradient cooling) and repumpimg beam induced geometric cooling, and they will be cooled to a few photon recoil limits (～2 μK) from MOT's temperature (～60 μK). Whereas in the Ar + hollow laser beam trap, cold atoms will be further cooled by Raman cooling (or velocity selection coherent population trapping) and compressed by a blue detuned covering beam. We have performed Monte Carlo simulations for PHB cooling process, calculated the optical potential for 133 Cs atoms in Ar + hollow laser beam, and estimated total collision loss and atomic density. Our study shows that the realization of an optically cooled and trapped BEC of 133 Cs atoms may be possible in our all optical dipole trap.