1 January 1992 Evanescent-wave spectroscopy down infrared transmitting optical fibers
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Proceedings Volume 1591, Infrared Fiber Optics III; (1992) https://doi.org/10.1117/12.56580
Event: OE Fiber, 1991, Boston, MA, United States
Abstract
The evanescent-wave spectrum of a sample surrounding the core of an optical fiber is a complex function of the optical constants of the media involved as well as the geometry of the sensing fiber. We develop a simple theory for evanescent-wave absorption in the weak absorption limit where we show that the absorbance of a length of sensor fiber may be related linearly to the bulk sample absorption coefficient. We present experimental data that verifies the observed scaling between the evanescent-wave absorbance and the bulk absorption coefficient for an isopropanol sample. The application of evanescent-wave spectroscopy with different sensor fiber materials is discussed, along with experimental and theoretical data for the enhancement of evanescent-wave spectroscopy using tapered fibers. Finally we discuss the results of a numerical series of calculations based on the exact ray paths of radiation within the fiber and the fundamental theory of ATR absorption at an interface assuming a plane wave approximation. In the more complex theory the evanescent-wave absorption coefficient is a decreasing function of the bulk absorption coefficient.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard D. Driver, Richard D. Driver, James N. Downing, James N. Downing, Garett M. Leskowitz, Garett M. Leskowitz, } "Evanescent-wave spectroscopy down infrared transmitting optical fibers", Proc. SPIE 1591, Infrared Fiber Optics III, (1 January 1992); doi: 10.1117/12.56580; https://doi.org/10.1117/12.56580
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