Abstract

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 $8.83\times {10}^{-16}$ at 1 s to $1.67\times {10}^{-19}$ at 1000 s, which indicates our proposed phase-locking system possesses ultrahigh measurement precision with good long-term stabilization performance.

© 2016 Optical Society of America