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 fib ers is introduced. As silver halides form soluble complexes with thiosulfat e in aqueous solution, the fiber can be chemically tapered by an etching pr ocess, which also warrants a high quality of the fiber surface. The evanesc ent field sensitivity of thus obtained tapered fibers was raised by more th an one order of magnitude, demonstrated by calibration curves of tetrachlor oethylene in hexane recorded with a tapered sensor fiber coupled to a Fouri er transform infrared (FT-IR) spertrometer.