Udommai Parinya, Harvey Matthew, Murray Andrew James
Photon Science Institute, Department of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, United Kingdom.
Rev Sci Instrum. 2021 Jul 1;92(7):073004. doi: 10.1063/5.0050169.
A digital system for controlling the frequency of a continuous wave (CW) ring laser is described. The system utilizes Doppler-free absorption to steer the laser onto a resonance peak within a vapor cell and can hold the laser at this frequency for long periods of time using active feedback. The vapor cell is immersed in a sinusoidally varying magnetic field that produces a feedback signal by exploiting the Zeeman effect so that the laser frequency does not need to be dithered to achieve lock. A bias field can also be applied to adjust the frequency over several MHz while maintaining lock. This is advantageous for cold atom studies that require the laser to be red-detuned from resonance. Signals from the absorption cell and magnetic field are digitized and fed to a dedicated microcontroller that calculates and produces the feedback signal. The digital control system is described, and measurements are presented where the locked frequency is compared to data obtained from a commercial wavemeter. The locked frequency standard deviations ranged from 250 to 450 kHz within a 1 h period. The Allan deviations of the locked frequency had the best stability at a value of 6 × 10 in a 10 s averaging period. The locking system described here has application in experiments that require very stable laser frequency control and can also be used for regular recalibration of wavemeter parameters. The design can easily be adapted to control different CW laser systems and hence can be used for a range of atomic targets.
本文描述了一种用于控制连续波（CW）环形激光器频率的数字系统。该系统利用无多普勒吸收将激光器引导至蒸汽池内的共振峰上，并可通过有源反馈将激光器长时间保持在该频率上。蒸汽池浸没在一个正弦变化的磁场中，该磁场利用塞曼效应产生反馈信号，从而无需对激光频率进行抖动即可实现锁定。还可以施加一个偏置场来在保持锁定的同时将频率调整几个兆赫兹。这对于需要将激光从共振频率进行红失谐的冷原子研究是有利的。来自吸收池和磁场的信号被数字化并馈送到一个专用微控制器，该微控制器计算并产生反馈信号。文中描述了该数字控制系统，并给出了将锁定频率与从商用波长计获得的数据进行比较的测量结果。在1小时内，锁定频率的标准偏差范围为250至450千赫兹。在10秒的平均周期内，锁定频率的阿伦偏差在6×10时具有最佳稳定性。这里描述的锁定系统可应用于需要非常稳定的激光频率控制的实验，也可用于波长计参数的定期重新校准。该设计可以很容易地进行调整以控制不同的连续波激光系统，因此可用于一系列原子目标。
