Synthetic reflection self-injection-locked microcombs

Laser-driven microresonators have enabled chip-integrated light sources with unique properties, including the self-organized formation of ultrashort soliton pulses and frequency combs (microcombs). While poised to impact major photonic applications such as spectroscopy, sensing and optical data processing, microcombs still necessitate complex scientific equipment to achieve and maintain suitable single-pulse operation. Here to address this challenge, we demonstrate microresonators with programmable synthetic reflection providing tailored injection feedback to the driving laser. Synthetic reflection achieves independence from random sample scattering properties and, when designed appropriately, enables deterministic access to self-injection-locked microcombs operating exclusively in the single-soliton regime. These results provide a route to easily operable microcombs at scale for portable sensors, autonomous navigation or extreme-bandwidth data processing. The novel concept of synthetic reflection may also be generalized to other integrated photonic systems. Photonic crystal microring resonators with a periodic corrugation inscribed along the resonator’s circumference allow programmable synthetic reflection for self-injection-locked microcombs and their operation exclusively in the single-soliton regime.