The ultra-stable laser system has been widely used in a variety of fields. Recently, automatic laser frequency stabilization is crucial to some unmanned applications. This paper reports the development of the automatic laser frequency stabilization for the ultra-stable laser system with hertz-level linewidth. The hybrid automatic frequency stabilization circuits are combined with analog high-speed PID circuits and digital automatic controller. An external cavity diode laser is demonstrated to be frequency locked to a reference cavity with a control bandwidth over 2.1 MHz which can be improved. Beating with a second ultra-stable lasers, a median linewidth of 3.86 Hz is obtained via 203 repeated measurements. To characterize the reliability of automatic frequency stabilization, the laser is intendedly interrupted by 4432 times, while the laser frequency is relocked automatically. The mean time for the laser relocking is 4.86 s, and 90 % of the experiments can be relocked within 6 s. Moreover, one week of laser frequency stabilization with automatic relocking is demonstrated. The design of the auto-locking laser system can be applied for field and space applications.

超稳定激光系统已广泛应用于各个领域。最近，自动激光频率稳定对一些无人应用至关重要。本文报道了具有赫兹级线宽的超稳定激光系统的自动激光频率稳定的发展。混合自动稳频电路与模拟高速PID电路和数字自动控制器相结合。外腔二极管激光器的频率锁定到参考腔，控制带宽超过 2.1 MHz，可以改进。使用第二个超稳定激光器进行跳动，通过 203 次重复测量获得 3.86 Hz 的中值线宽。为了表征自动稳频的可靠性，激光被有意中断 4432 次，同时自动重新锁定激光频率。激光重新锁定的平均时间为 4.86 s，90% 的实验可以在 6 s 内重新锁定。此外，还演示了具有自动重新锁定功能的一周激光频率稳定。自锁激光系统的设计可用于现场和空间应用。