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Proceedings Paper

Evanescent-wave spectroscopy down infrared transmitting optical fibers
Author(s): Richard D. Driver; James N. Downing; Garett M. Leskowitz
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Paper 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.

Paper Details

Date Published: 1 January 1992
PDF: 12 pages
Proc. SPIE 1591, Infrared Fiber Optics III, (1 January 1992); doi: 10.1117/12.56580
Show Author Affiliations
Richard D. Driver, Galileo Electro-Optics Corp. (United States)
James N. Downing, Galileo Electro-Optics Corp. (United States)
Garett M. Leskowitz, Galileo Electro-Optics Corp. (United States)

Published in SPIE Proceedings Vol. 1591:
Infrared Fiber Optics III
James A. Harrington; Abraham Katzir, Editor(s)

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