Stabilized C-Band Kerr Frequency Comb

We have designed and fabricated a Kerr frequency comb oscillator with 27.5 GHz repetition rate by pumping a whispering gallery mode crystalline resonator with a laser at 1560 nm center wavelength. The oscillator is stabilized to the Rb
⁸⁷
D
₂
line using frequency doubling with a periodically poled lithium niobate (PPLN) waveguide. Allan deviation of the repetition rate of the frequency comb was measured to be on the order of 10
^-11
at 1 s to 1000 s integration time. The long-term stability limitation is attributed to the frequency drift of the phase matching window of the PPLN structure as well as to mode interaction and associated drift of the resonator spectrum.