镱原子光频标中泵浦光特性的研究

许朋

镱原子光频标中泵浦光特性的研究

许朋

（皖北卫生职业学院，宿州 234000）

镱原子光频标中泵浦光参数的优化可以提高钟频率稳定度性能。通过分析镱原子能级分布的特点，建立了能级跃迁速率方程。采用数值计算方法求解速率方程，获得了泵浦时间与649 nm、770 nm、1388 nm泵浦光的光强和失谐的关系。比较了两种泵浦方法的效果，分析了泵浦时间的改变对钟频率稳定度性能的影响。理论计算的结果为实验确定泵浦光的光强、泵浦时间提供了重要的参考。

镱原子光频标；速率方程；泵浦光

0 引言

1 泵浦方案一分析

图1 镱原子的能级图

649 nm和770 nm泵浦光共同作用下，处于不同能级的原子数的变化方程如下[12-14]

图3 能级的原子数达到10 000时需要的泵浦时间t随649 nm和770 nm激光光强的变化

从图3可知，在649 nm激光光强> 5且770 nm激光光强> 1区域，泵浦时间不超过30 μs。综合计算的结果，一定条件下，我们取649 nm激光光强= 5，770 nm激光光强= 1。

图4 能级的原子数达到10 000时需要的泵浦时间t随激光失谐g和h的变化

图5 能级的原子数达到10 000时需要的泵浦时间t随649 nm和770 nm激光失谐的变化

从图5可知，649 nm激光和770 nm激光的失谐都在-400 MHz以内时，泵浦时间不超过10 ms。一般情况下，649 nm激光的失谐在-200 MHz以内且770 nm激光的失谐在-400 MHz以内时，泵浦时间不超过3 ms。随着649 nm激光失谐的增大，泵浦时间显著的变大。

最后分析一下649 nm和770 nm激光频率漂移引起的泵浦时间的变化d/MHz。假定649 nm和770 nm激光都偏离其对应跃迁的共振频率200 MHz，在这一点d/MHz的数值为：649 nm为21.9 μs/MHz，770 nm为0.1 μs/MHz。可知，泵浦时间随649 nm激光频率漂移变化较大。

2 泵浦方案二分析

图6 1 388 nm激光作为泵浦光时，镱原子的能级图

图7 能级的原子数达到稳态时需要的泵浦时间t随1 388 nm激光光强s的变化

从图8可知，1 388 nm激光失谐从0 MHz增加到-50 MHz时，从0.2 ms增加到21 ms。因此，1 388 nm激光的失谐不能较大，频率漂移要比较小，否则需要很长的时间才能完成原子的泵浦。

图8 能级的原子数达到稳态时需要的泵浦时间t随1 388 nm激光失谐ω的变化

3 讨论

4 总结

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The research of the characteristics of pump light in ytterbium atomic optical frequency standard

XU Peng

(North Anhui Health Vocational College, Suzhou 234000, China)

The optimization of the pump light parameters in the ytterbium atomic optical frequency standard can improve the clock frequency stability performance.By analyzing the characteristics of the energy level distribution of ytterbium atom, the energy level transition rate equation was established.The numerical calculation method was used to solve the rate equation, and the relationship between the pumping time and the intensity and detuning of the pump light at 649 nm, 770nm and 1 388 nm was obtained.The effects of the two pumping methods were compared, and the effect of changes in pumping time on the performance of clock frequency stability was analyzed.The results from our theoretical calculation provide an important reference for the experiment to determine the pump light intensity and pumping time.

ytterbium atomic optical frequency standard; rate equation; pump light

10.13875/j.issn.1674-0637.2021-02-0085-07

许朋. 镱原子光频标中泵浦光特性的研究[J]. 时间频率学报, 2021, 44(2): 85-91.

2020-10-15；

2020-12-05