Wang Ke-Mu, Du Zhi-Jing, Liu Yan-Yan, Yu Zhi-Jian, Yan Shu-Bin, Liu Tao, Dong Rui-Fang, Zhang Shou-Gang
Opt Express. 2021 Nov 8;29(23):38527-38539. doi: 10.1364/OE.440524.
Laser intensity noise is one of the main limiting factors in pulsed vapor cell clocks. To reduce the contribution of the laser intensity noise to detection signal in the pulsed optically pumped atomic clock, a scheme based on the differential Faraday rotation angle is proposed. Theoretically, the Ramsey fringes, the sensitivity of clock frequency to laser intensity fluctuation and the signal to noise ratio for absorption, differential, and Faraday rotation angle methods are calculated and compared. Using a Wollaston prism rotated 45°relative to the incident polarization, and two photodetectors, Ramsey fringes of three detection methods are obtained simultaneously. In the proposed scheme, the long-term Faraday rotation angle fluctuation is 0.66% at 30000s, which is much smaller than fluctuation of traditional absorption signal 3.9% at 30000s. And the contribution of laser intensity noise to clock instability is also reduced. Using optimized photodetector with high common mode rejection ratio, a better performance should be expected. This proposed scheme is attractive for the development of high performance vapor clock based on pulsed optically pumped.
激光强度噪声是脉冲汽态池时钟的主要限制因素之一。为了减少激光强度噪声对脉冲光泵浦原子钟中探测信号的影响，提出了一种基于差分法拉第旋转角的方案。从理论上计算并比较了拉比振荡条纹、时钟频率对激光强度波动的灵敏度以及吸收、差分和法拉第旋转角方法的信噪比。使用相对于入射偏振旋转45°的渥拉斯顿棱镜和两个光电探测器，同时获得了三种探测方法的拉比振荡条纹。在所提出的方案中，30000秒时的长期法拉第旋转角波动为0.66%，远小于传统吸收信号在30000秒时3.9%的波动。并且激光强度噪声对时钟不稳定性的影响也降低了。使用具有高共模抑制比的优化光电探测器，有望获得更好的性能。该方案对基于脉冲光泵浦的高性能汽态钟的发展具有吸引力。
