Chalcogenide Fiber and Microcavity Platforms for Mid-Infrared Sensing and Nonlinear Photonics

Chalcogenide glasses are versatile mid-infrared (MIR) photonic materials because they combine broad infrared transparency, high refractive index, strong third-order nonlinearity, and processability into fibers, microfibers, planar waveguides and microcavities. This review examines chalcogenide fiber, waveguide, and microcavity platforms for MIR sensing and nonlinear photonics from a system-level perspective. We discuss material families, processing routes and device-relevant loss mechanisms; review fiber evanescent-wave spectroscopy, structured and functionalized fiber probes, microfibers, planar waveguides, resonators and suspended high-overlap waveguide sensors; and analyze nonlinear and active chalcogenide fibers and high-Q microcavities as MIR source platforms. Emphasis is placed on the transition from single-pass evanescent absorption to Q–overlap co-design and from isolated component demonstrations to source–waveguide–cavity–sensor–detector integration for compact molecular spectroscopy.