Optical Frequency Comb Generated with an Amplitude Modulated Pump in Silicon Nitride Ring-resonators

The coherence of the repetition-rate of optical frequency combs when generated using an amplitude modulated pump is experimentally investigated. We show that the repetition-rate of the frequency comb exhibit a linewidth of similar to 25 Hz even when the mismatch between the modulation frequency and the resonator free-spectral range is larger than the linewidth of the resonances of the ring-resonator.