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Proceedings Paper

Optimizing the optics for evanescent wave analysis with laser diodes (EWALD) for monitoring chlorinated hydrocarbons in water
Author(s): Joachim F. Kastner; Maurus Tacke; S. Silverstein; Abraham Katzir
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Paper Abstract

Fiber evanescent field analysis (FEFA) is a novel promising sensing technique for on-line and in situ analysis of hydrocarbons in water. With a conventional IR light source and FTIR spectroscopy it allows multicomponent analysis, while using MIR-tunable diode lasers results in more sensitive and faster single component analysis. Compared to common attenuated total reflection elements, silver halide (AgCl/Br) fibers offer more convenient application for remote sensing and field measurements because the fibers can be used for both, guidance of MIR radiation to and from the sensing part, and the sensing part itself. At present these fibers are multimode. The sensor response can be expected to depend strongly on the mode distribution in the fiber. We hence performed a model calculation that allows us to compare the FEFA absorption and the intrinsic fiber losses for given mode distributions and dependent on the optical parameters such as the coupling conditions and the fiber design. In order to link theoretical results to experimental data, the theory is based on an internal mode distribution derived from far field fiber emission data. We present far field data and the resulting internal distributions.

Paper Details

Date Published: 26 August 1996
PDF: 13 pages
Proc. SPIE 2783, Micro-Optical Technologies for Measurement, Sensors, and Microsystems, (26 August 1996); doi: 10.1117/12.248499
Show Author Affiliations
Joachim F. Kastner, Fraunhofer-Institut fuer Physikalische Messtechnik (Germany)
Maurus Tacke, Fraunhofer-Institut fuer Physikalische Messtechnik (Germany)
S. Silverstein, Tel Aviv Univ. (Israel)
Abraham Katzir, Tel Aviv Univ. (Israel)


Published in SPIE Proceedings Vol. 2783:
Micro-Optical Technologies for Measurement, Sensors, and Microsystems
Olivier M. Parriaux, Editor(s)

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