通过实验和理论相结合的方式,从热透镜效应角度研究了Er ³⁺,Yb ³⁺∶glass在激光二极管(LD)端面抽运条件下的激光输出能量,建立起LD抽运重复频率、Er ³⁺,Yb ³⁺∶glass热光系数与空腔运转斜率效率、调Q输出脉冲能量之间的关系。采用平凹腔结构,并以Co ²⁺∶MgAl₂O₄作为调Q开关,设计了LD端面抽运被动调Q激光器,实验结果发现,当热焦距大于前腔面光斑半径最小值对应的热焦距时,空腔运转斜率效率与材料的热光系数呈负相关,调Q输出脉冲能量与热光系数及抽运重复频率均呈负相关。基于理论研究,通过热焦距公式、稳定谐振腔的矩阵计算法以及被动调Q的速率方程进行数值模拟,解释并验证上述实验现象。结果显示,可通过降低抽运重复频率和选择低热光系数的Er ³⁺,Yb ³⁺∶glass等方式降低热透镜效应实现高脉冲能量的输出。

The Ramsey fringe contrast of a pulsed optically pumped cold atom clock is strongly affected by the transverse decay of the atomic sample. This letter calculates the Ramsey fringe with focus on transverse decay, and analyzes the Ramsey fringe contrast with different transverse decay rates. By fitting the experimental data, we obtain the transverse decay rate in a cold atom sample at an approximate value of 30.5 s-1, which is much smaller than that in a cell.

报道了一种新的测量大尺度冷原子团温度的方法。这种方法利用反亥姆霍兹线圈产生四极磁场，探测光沿着竖直方向逐点测量冷原子团的分布情况，获得冷原子团在不同自由下落时间下的密度分布曲线，进而拟合出冷原子团的温度值。通过实验，利用这种方法测量了积分球中冷原子团的温度，为73±12 μK，并与飞行时间(TOF)方法的测量结果进行了比较。

We cool 85Rb atoms in an integrating sphere directly from a vapor background using diffuse light generated by multiple reflections of laser beams in the inner surface of the integrating sphere. We compare and analyze the different features of cold 85Rb atoms and cold 87Rb atoms in diffuse light cooling, which are important in applying 85Rb and 87Rb isotopes in many experiments on testing fundamental physics.

Cold ⁸⁷Rb atom's loading in an integrating sphere with diffuse light is analyzed theoretically and experimentally. The experimental results show that diffuse light cooling has the greatest efficiency to cool the most atoms when the red detuning between the frequencies of cooling light and atom transition is about 3.3\Gamma (\Gamma is the natural linewidth, 6.065 MHz). Theoretical analysis using rate equation and numerical calculations on the cold atom number and loading time agree with the experimental results. This integrating sphere cooling would be a novel method for cooling atoms and lead to a new and robust cold atom source for atomic clock.