Chemically Tapered Silver Halide Fibers: An Approach for Increasing the Sensitivity of Mid-Infrared Evanescent Wave Sensors

In this work an innovative etching technique for tapering silver halide fibers is introduced. As silver halides form soluble complexes with thiosulfate in aqueous solution, the fiber can be chemically tapered by an etching process, which also warrants a high quality of the fiber surface. The evanescent field sensitivity of thus obtained tapered fibers was raised by more than one order of magnitude, demonstrated by calibration curves of tetrachloroethylene in hexane recorded with a tapered sensor fiber coupled to a Fourier transform infrared (FT-IR) spectrometer.