基于光学锁相环的高稳定度激光稳频方法研究

报道了一种基于光学锁相环的高稳定度激光稳频方法,用于提高可调谐外腔半导体激光器(TECDL)的频率稳定度和准确度。自行研制的光学锁相环电路采用数字鉴相与差分运算相结合的方式获得高灵敏度的鉴频鉴相误差信号,并通过高速模拟PID实现整个系统的闭环锁定。利用该光学锁相环系统进行了TECDL偏频锁定至光学频率梳(OFC)的实验,实验结果表明环路锁定后拍频频率波动在±0.3Hz范围内,偏置频率为50MHz时,光学锁相环系统在1s和1000s积分时间的相对阿伦方差分别为1.5×10^-9和8.5×10^-13。系统锁定后,拍频线宽由500kHz压缩至2kHz。该研究表明采用基于光学锁相环的激光稳频方法可以实现亚Hz级的激光频差控制,通过将TECDL偏频锁定至高稳定度的参考激光源可显著提高其频率稳定度,使其能够满足超精密测量、冷原子/离子干涉测量等领域对激光频率稳定度和准确度的要求。

Research on High Stability Laser Frequency Stabilization Method Based on Optical Phase-Locked Loop

A high stability laser frequency stabilization method based on optical phase-locked loop is reported to improve the frequency stability and accuracy of a tunable external cavity semiconductor laser (TECDL). Self-developed optical phase-locked loop circuit adopts the combination of digital phase discrimination and difference operation to obtain the high sensitivity frequency phase discrimination error signal, and realizes the closed-loop locking of the whole system through high-speed analog PID. Experimental results of TECDL offset locking to optical frequency comb (OFC) show that the frequency fluctuation is within ±0.3Hz after the loop locking. When the offset frequency is 50MHz, the Allan deviation of OPLL system of 1 s and 1000 s integration time is 1.5×10^-9 and 8.5×10^-13, respectively. The research shows that the sub-Hz laser frequency difference control can be realized by using the laser frequency stabilization method based on optical phase-locked loop. By offset locking the TECDL to the reference laser source with high stability, its frequency stability can be significantly improved, so that it can meet the requirements of laser frequency stability and accuracy in the fields of ultra-precision measurement and cold atom/ion interferometry.