A stabilized chip-scale Kerr frequency comb via a high-Q reference   photonic microresonator
  We stabilize a chip-scale Si3N4 phase-locked Kerr frequency comb via locking the pump laser to an independent stable high-Q reference microresonator and locking the comb spacing to an external microwave oscillator. In this comb, the pump laser shift induces negligible impact on the comb spacing change. This scheme is a step towards miniaturization of the stabilized Kerr comb system as the microresonator reference can potentially be integrated on-chip. Fractional instability of the optical harmonics of the stabilized comb is limited by the microwave oscillator used for comb spacing lock below 1 s averaging time and coincides with the pump laser drift in the long term. 
Jinkang Lim, Shu-Wei Huang, Abhinav K. Vinod, Parastou Mortazavian,   Mingbin Yu, Dim-Lee Kwong, Anatoliy A. Savchenkov, And...
physics.optics