利用取样积分实现激光饱和吸收一次谐波稳频

First Harmonic Saturated Absorption Frequency Stabilization of Lasers Using Sampling Integration Technique

对激光器进行频率调制,检测原子分子饱和吸收信号中的一次谐波成分得到频率误差信号,反馈控制可以实现激光频率的稳定。介绍了取样积分提收一次谐波信号的原理和利用单片机实现的取样积分和数字比例积分微分(PID)控制的技术。相对于传统的锁相放大和模拟PID技术,取样积分和数字PID结构简单,可靠性高,调试方便,实现难度大大降低。建立的Cs原子饱和吸收外腔半导体激光(ECDL)稳频系统,估算相对频率波动优于1.2×10-9(p-p),平均锁定时间可达7天,并实现了自动扫描饱和吸收峰、自动锁定和意外失锁的自动重新锁定功能。

If the frequency of a laser is modulated sinusoidally, the first harmonic component of saturated absorption signal can be used as error signal to stabilize the frequency of the laser. We introduce the principle of using sampling integration technique to obtain the first harmonic signal and the realization of sampling integration and digital proportional-integral differential （PID） controller by means of a microprocessor. Compared to traditional lock-in amplifiers and analog PID controllers, the new technique is more reliable in performance, simpler in construction and easier to be realized. An external-cavity diode laser （ECDL） frequency stabilization system is built with this sampling integration based on Cs atom saturated absorption. Relative frequency fluctuation better than 1.2 × 10^-9 （p-p） can be achieved and the average locking duration is about 7 days. The system can also automatically scan the saturated absorption peaks, lock to the desired peak and resume locking when lock is broken by accident.