Long-term phase-locking technique for locking the repetition rate of an optical frequency comb laser with...

An ultrahigh stable phase-locked loop system for synchronization of an optical frequency comb to a hydrogen maser has been proposed and experimentally demonstrated. A mathematical model has been set up to investigate the feasibility and steady state of the phase-locking system. The fractional frequency instability is evaluated by measuring the mixed-phase signal of an improved experimental system. Experimental results show that the fractional frequency instability of the phase-locked loop system lies from 8.83×10^-16 at 1 s to 1.67×10^-19 at 1000 s, which indicates our proposed phase-locking system possesses ultrahigh measurement precision with good long-term stabilization performance.