Enhancing the stabilizing robustness for optical frequency comb

We propose and demonstrate a method to promote the robustness for the stabilized optical frequency comb (OFC) referenced on the microwave atomic clock. The phase-locked loop (PLL) for the repetition rate of the OFC uses the charge-pump phase-frequency detector (CPPFD) instead of a double-balanced mixer (DBM), which serves as the phase detector in the traditional OFC locking schemes. The phase noise performance of the CPPFD scheme is achieved to the same level as the traditional DBM scheme, while the capture range of the PLL is significantly broadened. This greatly enhances the robustness of the stabilized OFC without degrading the noise performance.