  Photonic integrated circuits utilize planar waveguides to process light on a
chip, encompassing functions like generation, routing, modulation, and
detection. Similar to the advancements in the electronics industry, photonics
research is steadily transferring an expanding repertoire of functionalities
onto integrated platforms. The combination of best-in-class materials at the
wafer-level increases versatility and performance, suitable for large-scale
markets, such as datacentre interconnects, lidar for autonomous driving or
consumer health. These applications require mature integration platforms to
sustain the production of millions of devices per year and provide efficient
solutions in terms of power consumption and wavelength multiplicity for
scalability. Chip-scale frequency combs offer massive wavelength
parallelization, holding a transformative potential in photonic system
integration, but efficient solutions have only been reported at the die level.
Here, we demonstrate a silicon nitride technology on a 100 mm wafer that aids
the performance requirements of soliton microcombs in terms of yield, spectral
stability, and power efficiency. Soliton microcombs are reported with an
average conversion efficiency exceeding 50%, featuring 100 lines at 100 GHz
repetition rate. We further illustrate the enabling possibilities of the space
multiplicity, i.e., the large wafer-level redundancy, for establishing new
sensing applications, and show tri-comb interferometry for broadband
phase-sensitive spectroscopy. Combined with heterogeneous integration of
lasers, we envision a proliferation of high-performance photonic systems for
applications in future navigation systems, data centre interconnects, and
ranging.
