Octave-spanning frequency comb generation in a silicon nitride chip

We demonstrate a frequency comb spanning an octave via the parametric process of cascaded four-wave mixing in a monolithic, high-Q silicon nitride microring resonator. The comb is generated from a single-frequency pump laser at 1562 nm and spans 128 THz with a spacing of 226 GHz, which can be tuned slightly with the pump power. In addition, we investigate the RF amplitude noise characteristics of the parametric comb and find that the comb can operate in a low-noise state with a 30 dB reduction in noise as the pump frequency is tuned into the cavity resonance.