用于POP铷原子钟的DFB激光器自动稳频技术研究

Automatic frequency stabilization system of DFB diode laser for POP Rb atomic clock

针对传统手动稳频需要有人值守的弊端,基于饱和吸收谐波稳频的原理,设计了一套可实现对分布反馈式(distributed feedback,DFB)半导体激光器频率长期锁定的自动稳频系统。整套系统以STM32微控制器为核心,在此基础上进行自动稳频软件程序设计,具有体积小和抗干扰强的特点。经实验测试,该系统能够实现自动稳频,并在失锁后快速自动回锁。在实验室环境下,连续稳定工作超过一个月仍然保持锁定状态,失锁后能在1 s内重新锁定,锁定后线宽为5 MHz。作为抽运和探测光源,DFB激光器长期连续锁定的实现,为实现脉冲激光抽运(pulsed optically pumped,POP)铷原子钟在空间应用环境下长期无人干预稳定运行奠定了技术基础。

With the purpose of avoiding the shortcoming of the traditional manual frequency stabilization system which needs to be attended manually, a compact digital automatic frequency stabilization system is proposed, based on the theory of the saturated absorption harmonic frequency stabilization, which can keep the DFB diode laser frequency locked to a rubidium line(795 nm) for a long time. The STM32 micro controller, being the core component of the system, lays the hardware foundation of digital loop software design, and the system is characterized by small volume and strong anti-interference capacity. The experimental test indicated that the system can automatically achieve frequency stabilization and quickly relock the diode laser. Under the laboratory environment, the DFB diode laser can be locked to Rb line stably and continuously for more than a month and relocked again within one second, with a bandwidth of 5 MHz. The DFB diode laser is used to be as the pumping and detecting laser source of POP Rb atomic clock, and the realization of its long-time automatic stabilization makes it possible that the POP Rb atomic clock works stably for long time without manned intervention under the space-borne circumstance.