Implementation of an Active Control System for Kerr Optical Soliton Frequency Comb Based on FPGA

Due to their millimeter-scale size and low pump power threshold, Kerr optical soliton frequency combs have emerged as a key technology for chip-scale optical atomic clock research. However, the abrupt intracavity power drop during Kerr optical soliton formation leads to cavity frequency drift, which significantly shortens the lifetime of Kerr optical soliton frequency combs. Some active control methods have been reported for long-term stabilization of Kerr solitons, such as soliton power control, Pound-Drever-Hall frequency locking, and auxiliary laser mode. However, the electronic control systems used for these methods are rarely reported. This work presents an active control system for stabilizing Kerr optical soliton frequency combs based on Field-Programmable Gate Array (FPGA). It achieves long-term stable operation of Kerr optical soliton combs in both MgF₂ and CaF₂ microresonators by power control and PDH frequency locking. Furthermore, the system can be extended to other microresonator platforms (e.g., Si₃N₄, AlN, SiO₂) for Kerr optical soliton frequency generation and stabilization.