A low-latency digital servo for optical frequency comb stabilization

As a fundamental tool in precision spectroscopy and metrology, the optical frequency comb demands exceptional stability and accuracy across diverse applications. Digital servo systems, offering advantages such as low cost and high flexibility, are increasingly employed for optical frequency comb stabilization; however, their performance is constrained by the limited control bandwidth. In this work, we present a low-latency digital servo system designed for optical frequency comb stabilization. The system is implemented on a custom-designed field-programmable gate array-based digital board. Through the optimization of filtering and phase detection algorithms, computational latency is reduced while maintaining precision, enabling a control bandwidth of 1.1 MHz. The repetition rate of the optical frequency comb is locked to a 1560 nm ultra-stable laser. The modified Allan deviation of the measured beat signal, normalized to the optical frequency, is 7.27 × 10-18 at 1 s, thereby validating the performance of the proposed digital servo system.