Hybrid InP and SiN integration of an octave-spanning frequency comb.

Implementing optical-frequency combs with integrated photonics will enable wider use of precision timing signals.Here, we explore the generation of an octave-span, Kerr-microresonator frequency comb, using hybrid integration ofan InP distributed-feedback laser and a SiN photonic-integrated circuit. We demonstrate electrically pumped and fiber-packaged prototype systems, enabled by self-injection locking. This direct integration of a laser and a microresonatorcircuit without previously used intervening elements, like optical modulators and isolators, necessitates understand-ing self-injection-locking dynamics with octave-span Kerr solitons. In particular, system architectures must adjust tothe strong coupling of microresonator back-scattering and laser-microresonator frequency detuning that we uncoverhere. Our work illustrates critical considerations towards realizing a self-referenced frequency comb with integratedphotonics.