中性汞原子磁光阱装载率的优化  

Optimization of the loading rate of magneto-optical trap for neutral mercury atom

作　　者：苟维 刘亢亢[1,2] 付小虎[1,2] 赵儒臣 孙剑芳[1,2] 徐震[1,2,3] 

机构地区：[1]中国科学院上海光学精密机械研究所,量子光学重点实验室,上海201800 [2]中国科学院大学,北京100049 [3]中国科学院冷原子物理中心,上海201800

出　　处：《物理学报》2016年第13期1-7,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:91436105,11547251)资助的课题~~

摘　　要：量子投影噪声是影响光晶格钟的一个重要参数,提高磁光阱中装载率有利于降低量子投影噪声,可提升光晶格钟的性能.针对实验所用的汞原子单腔磁光阱,本文分析并计算了磁光阱中汞原子受力情况和一维运动规律,在此基础上用随机数方法对磁光阱中汞原子三维装载进行了数值计算,获得了磁光阱中的稳态原子数,研究了磁光阱的冷却激光的光强、失谐量以及磁场梯度等参数对稳态原子数的影响,得出了获得最优装载率的实验参数.涉及的计算方法和结论对汞原子光晶格钟的实验设计具有参考价值.Optics lattice clock is a hot topic in the researches of frequency standard and metrology. Neutral mercury atom is one of the most promising candidates for optical lattice clock. Due to its large atomic number, mercury atom is insensitive to black body radiation, which is the severe limitation for developing the optical lattice clocks. To realize the optical lattice clock of neutral mercury atoms, the first step is to implement laser-cooling and trapping of neutral mercury atoms. The cooling transition of mercury atom is1S0–3P1transition. The wavelength is 253.7 nm, the line width is 1.27 MHz, and the saturation intensity is 10.2 m W/cm2. Quantum projection noise（QPN） is an important parameter that affects optical lattice clock. Increasing the loading rate of magneto-optical trap（MOT） can help lower the QPN, thereby improving the performance of optical lattice clock. In this work, we calculate the scattering force of deep UV cooling laser, which is exerted on mercury atom in our single chamber MOT, and numerically simulate the onedimensional motion of the atom in the MOT. It gives us the capture velocity under optimized parameters of the MOT.Then we calculate the loading rate of three-dimensional MOT by a high efficient random sampling method. According to the rate equation of MOT, the loading rate is proportional to the atom number of the steady state, which is the accessible parameter in the experiment. An experimental setup of MOT is established with a high vacuum system and a frequency quadrupled semiconductor laser system. The fluorescence imaging on an EMCCD gives the atom number in the MOT.We also calibrate the vapor density of background mercury gas in the vacuum, and measure the atom number in a steady MOT. We numerically simulate and experimentally study the influences on the atom number on the parameters of MOT, such as laser intensity, laser detuning and magnetic field gradient. The calculated results are in consistent with the experimental results. We also find the optimized parameters to m

关 键 词：汞原子 磁光阱 光晶格钟 激光冷却 

分 类 号：O562[理学—原子与分子物理]