  Silicon photonics enables wafer-scale integration of optical functionalities
on chip. A silicon-based laser frequency combs could significantly expand the
applications of silicon photonics, by providing integrated sources of mutually
coherent laser lines for terabit-per-second transceivers, parallel coherent
LiDAR, or photonics-assisted signal processing. Here, we report on
heterogeneously integrated laser soliton microcombs combining both InP/Si
semiconductor lasers and ultralow-loss silicon nitride microresonators on
monolithic silicon substrate. Thousands of devices are produced from a single
wafer using standard CMOS techniques. Using on-chip electrical control of the
microcomb-laser relative optical phase, these devices can output single-soliton
microcombs with 100 GHz repetition rate. Our approach paves the way for
large-volume, low-cost manufacturing of chip-based frequency combs for
next-generation high-capacity transceivers, datacenters, space and mobile
platforms.
