Mid-Infrared Waveguides: A Perspective.

Significant advancements in waveguide technology in the mid-infrared (MIR) regime during recent decades have assisted in establishing MIR spectroscopic and sensing technologies as a routine tool among nondestructive analytical methods. In this review, the evolution of MIR waveguides along with state-of-the-art technologies facilitating next-generation MIR chem/bio sensors will be discussed introducing a classification scheme defining three "generations" of MIR waveguides: (1) conventional internal reflection elements as "first generation" waveguides; (2) MIR-transparent optical fibers as "second generation" waveguides; and most recently introduced(3) thin-film structures as "third generation" waveguides. Selected application examples for these each waveguide category along with future trends will highlight utility and perspectives for waveguide-based MIR spectroscopy and sensing systems.