Mid-Infrared Molecular Sensing

Abstract

Mid-infrared (MIR)mid-infrared (mid-IR) sensing has wide applicability for detecting molecular solids, liquids, solutions and gases. This chapter reviews how guided waves in MIR-transmitting chalcogenide glass fibers, waveguides and resonators are showing promise for compact, portable and real-time molecular sensing with potential use across many sectors, such as in medicine, security, the environment, agriculture, pharmaceuticals and in manufacturing and chemical processing. New bright, MIR supercontinuum laser sources have been demonstrated both in chalcogenide glass fiber and on-chip for wideband MIR molecular sensing. Also, bright rare earth-doped chalcogenide glass fiber photoluminescence (photoluminescence (PL)) is being harnessed in PL-absorption narrow-band MIR molecular sensing. Many designs of chalcogenide glass sensor heads realized for evanescent field detection of molecules both in fiber and on-chip are described in this chapter. Also, processing of chalcogenide glasses pertinent to application in MIR molecular sensing devices is presented. The necessary background to MIR optical sensing is given, showing how it can be quantitative, of high contrast, fast and with high sensitivity and specificity. The data processing required to interpret MIR molecular sensing is briefly discussed.