An advanced digital controller with automatic design for laser frequency stabilization in space

We present an advanced digital controller developed for laser frequency stabilization systems. A fully digital Pound–Drever–Hall (PDH) control scheme is implemented through direct digitization of the modulated optical signal, which is then demodulated in the digital domain and employs an inner–outer loop control module to lock the laser frequency to the cavity resonance. The design features automatic locking and relocking, where complex logic for signal verification and time-consuming monitoring is implemented using a state machine, thus enabling the system to automatically recover and prevent the locking procedure from getting stuck in a particular step. We also introduce a locked-state determination method based on spectral characteristic of closed-loop noise. Using fast Fourier transform (FFT) analysis and in-loop noise power evaluation, the locking state can be accurately determined within 8 milliseconds, eliminating the need for threshold selection. This research significantly advances autonomous optical control systems by demonstrating a highly efficient, reliable, and versatile PDH control system with strong potential for future space applications.