Silicon Nitride Microcombs: From Microcavity Fabrication to Emerging Applications

ABSTRACT Silicon nitride (Si 3 N 4 ) has emerged as a pivotal platform in nonlinear integrated photonics, owing to its ultralow linear loss, high refractive index, and intrinsic Kerr nonlinearity. These remarkable attributes have particularly stimulated extensive research on the fabrication of Si 3 N 4 ‐based integrated microresonators and the applications of on‐chip microcombs. This review presents an overview of Si 3 N 4 microcombs, including microresonator fabrication, soliton generation mechanisms, emerging applications, and future development. First, the review introduces the fabrication process of Si 3 N 4 microcavities, as well as their performance and optimization. Second, two representative generation approaches for soliton microcombs are discussed comprehensively, with emphasis on their underlying principles, implementation strategies, and respective influences on the generation of dissipative solitons and associated comb states. In addition, some novel solitons are introduced to show the diversity and functionality of Si 3 N 4 microcombs. Finally, the current applications and future prospects of Si 3 N 4 soliton microcombs are discussed, highlighting high‐speed optical communication, spectroscopy, detection, and metrology.