Octave-Spanning Kerr Frequency Comb in a Si₃N₄ Microresonator at Electronically Detectable Repetition Rate

A key challenge in microresonator-based frequency combs has been achieving f-2f self-referencing, which requires a powerful, octave-spanning microcomb. Stable self-referenced combs have numerous applications including ultra-low-noise microwave generation and optical-atomic clocks [1]. Other methods for generating octave-spanning spectra often involve additional processes, including such as comb shaping, amplification, dispersion control, or the integration of a separate platform utilizing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\chi^{(2)}$</tex> materials [2]. In our approach, we use a single resonator pumped by picosecond pulses synchronized to the resonator's repetition rate and long directional couplers to achieve high coupling rates for higher-order dispersive waves at high frequencies.