频率稳定的激光器在精密计量、高分辨率光谱等许多领域具有重要的应用。使用KTP晶体将Nd:YAG激光器输出的激光(1064 nm)倍频到532 nm，采用波长调制吸收光谱技术获得吸收峰的一次谐波信号作为鉴频信号，并基于数字比例积分微分(PID)反馈控制技术，把倍频后的频率稳定在碘分子B-X态(32-0)带的R(56)吸收峰上，在1 h的连续测量时间内，频率漂移幅度小于2 MHz，远小于多普勒受限的光谱线宽，频率稳定度达到了10-9量级，整套系统可以实现长时间连续工作。使用的数字PID稳频方案，可以有效抑制激光的长期频率漂移，具有方案简单、易于实现的优点，同时显著降低了较大幅度随机噪声对系统稳定性的影响。

Frequency stabilized lasers are very important in many fields such as precision metrology and high resolution spectroscopy. A Nd:YAG laser (1064 nm) frequency stabilization scheme is reported. In this scheme, the laser frequency is doubled and stabilized at the R(56) absorption line of (32-0) band in the B-X system of molecular iodine based on digital proportion-integration-differentiation (PID) technique. The frequency stability reaches 10-9 and the frequency drift is less than 2 MHz in 1 h, which is far less than the Doppler-limited molecular absorption linewidth. This scheme can suppress the laser frequency drift effectively and minimize the large-amplitude random noise. It is proved simple and easy to implement.