Foundry manufacturing of octave-spanning microcombs

Abstract

Soliton microcombs provide a chip-based, octave-spanning source for self-referencing and optical metrology. We use a silicon nitride integrated photonics foundry to manufacture 280 single-chip solutions of octave-spanning microcombs on a wafer. By group-velocity dispersion (GVD) engineering with the waveguide cross section, we shape the soliton spectrum for dispersive-wave spectral enhancements at the frequencies for f-2f self-referencing. Moreover, we demonstrate the other considerations, including models for soliton spectrum design, ultra-broadband resonator external coupling, low-loss edge couplers, and the nonlinear self-interactions of few-cycle solitons. To cover the fabrication tolerance, we systematically scan 336 parameter sets of resonator width and radius, ensuring at least one device on each chip can yield an octave-spanning comb with an electronically detectable carrier-envelope offset frequency, which has been supported by our experiment. Our design and testing process permit highly repeatable creation of single-chip solutions of soliton microcombs optimized for pump operation ∼100 mW and high comb mode power for f-2f detection, which is the central component of a compact microsystem for optical metrology.