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中国物理学会期刊

极化角依赖的铯原子魔术波长光阱理论分析

CSTR: 32037.14.aps.72.20222268

Theoretical analysis of polarization-angle-dependent magic-wavelength optical dipole trap of Cs atoms

CSTR: 32037.14.aps.72.20222268
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  • 在对经激光预冷却的原子进行俘获的光学偶极阱中, 魔术波长光学偶极阱可以消除所关心的两原子态间跃迁的差分光频移, 使得光子在原子态间的跃迁频率与自由空间相同, 对于提高实验重复率、减弱原子的退相干具有重要意义, 使其在冷原子物理、量子光学、精密测量等领域已成为越来越重要的技术手段. 本文基于多能级模型理论计算了耦合铯原子D2线的6S1/2基态和6P3/2激发态对光阱激光波长(800—1000 nm)依赖的动态电极化率, 得到了俘获基态和激发态的光阱激光的魔术波长. 由于角动量大于0.5的原子态的极化率对极化角非常敏感, 本文以线偏振光阱激光为例, 讨论并分析了魔术波长与相应的魔术极化率对极化角的依赖关系, 得到了魔术极化角为54.7°以及该角度下的魔术波长分别为886.4315 nm与934.0641 nm, 进一步分析了这两种情况下魔术条件的鲁棒性与实验操作的可行性.

     

    Laser cooling and trapping of neutral atoms is of great significance for studying the physical and chemical properties of atoms. To further realize the spatial localization of atoms, optical dipole trap (ODT) was proposed to manipulate individual atoms, ions or molecules and has become an increasingly important technique in the field of cold atomic physics and quantum optics. To eliminate the differential light shift of transitions between atomic states, ODT can be turned off during excitation/radiation. However, it will shorten the trap lifetime of the atom and reduce the repetition rate of the single photon. The AC stark shift can be eliminated experimentally by constructing blue-detuned dark ODT, but the micron-level dark ODT usually requires more complex experimental equipment and is not easy to operate. Therefore, magic-wavelength ODT was constructed to realize that the transition frequency of photons between atomic states is the same as in free space. When the trapping laser makes the differential light shift of the transition between the two atomic states zero, the laser wavelength is called the magic wavelength. The magic-wavelength ODT can eliminate the differential light shift of the transition between atoms, improve the repetition rate of the experimental sequence and weaken the atomic decoherence. In recent years, it has become a powerful tool for manipulating cold atoms, especially for coherently manipulating the atomic inner states. In the present work, with the theory of multi-level model, we calculate the dynamic electric polarizability of the 6S1/2 ground state and the 6P3/2 excited state connecting the D2 line of cesium atom in a range of 800–1000 nm, and obtain the magic wavelength of the optical trapping laser to trap the ground state and the excited state. Since the polarizability of atomic states with angular momentum greater than 0.5 is very sensitive to the polarization angle, the polarization-angle-dependent magic wavelength and the corresponding magic polarizability are analyzed by taking the linearly-polarized trapping laser for example. The magic polarization angle is 54.7° and the magic wavelength at this angle are 886.4315 and 934.0641 nm, respectively. The robustness of the magic conditions and the feasibility of the experimental operation are further analyzed.

     

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