Silicon‐Nitride‐Integrated Hybrid Optical Fibers: A New Platform for Functional Photonics

Abstract Hybrid optical fibers that integrate exotic materials within more traditional silica glass architectures open a route for the development of highly functional all‐fiber photonic systems. Here, a compact hybrid optical fiber platform is reported formed by depositing a silicon nitride (SiN x ‐ nitride‐rich) nanolayer onto the surface of fused‐silica microfibers via plasma‐enhanced chemical vapor deposition. The SiN x thickness can be precisely tuned over a range of tens of nanometers, while maintaining an ultra‐smooth deposition surface, allowing for tunable coupling between the modes guided predominantly in the nanolayer and the fiber core. The effective indices of the hybrid modes display an anti‐crossing behavior under resonant conditions, resulting in a rich dispersion landscape that can be tailored via adjusting the SiN x thickness. By fabricating a SiN x ‐silica hybrid microfiber with precise dispersion engineering and a low insertion loss, a flat supercontinuum spectrum spanning >1.5 octaves (−20 dB level) has been generated. The results demonstrate that SiN x ‐silica hybrid microfibers can offer a unique combination of broadband transmission and wide tunablity of the mode properties, while still retaining the benefits of robust integration with conventional silica glass fiber networks, providing a rich playground for hybrid fiber‐based photonic systems.