300 mm wafer-scale SiN platform for broadband soliton microcombs compatible with alkali atomic references

Chip-integrated optical frequency combs (OFCs) based on Kerr nonlinear resonators are of great significance given their scalability and wide range of applications. Broadband on-chip OFCs reaching visible wavelengths are especially valuable as they address atomic clock transitions that play an important role in position, navigation, and timing infrastructure. Silicon nitride (SiN) deposited via low-pressure chemical vapor deposition (LPCVD) is the usual platform for chip-integrated OFCs, due to its low absorption and repeatable dispersion, and such fabrication is now standard at wafer sizes up to 200 mm. However, the LPCVD high temperature and film stress pose challenges in scaling to larger wafers and integrating with electronic and photonic devices. Here, we report the linear performance and broadband frequency comb generation from microring resonators fabricated on 300 mm wafers at AIM Photonics, using a lower temperature, lower stress plasma-enhanced chemical vapor deposition process suitable for thick (≈700 nm) SiN films and compatible with electronic and photonic integration. The platform exhibits consistent insertion loss, high intrinsic quality factor, and thickness variation of ±2% across the whole 300 mm wafer. We demonstrate broadband soliton microcomb generation with a lithographically tunable dispersion profile extending to wavelengths of common alkali atom transitions. These results are a step towards more highly integrated and mass-manufacturable devices, enabling advanced applications including optical clocks, LiDAR, and beyond.