7 December 2004 Groundwater monitoring of VOCs with an interferometric optical waveguide sensor
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Abstract
Planar waveguides have evanescent fields sensitive to index of refraction changes in the volume immediately above the waveguide surface. These fields extend up to 5000 Å above the surface. Placing a chemically sensitive polymer film within this region provides the basis for a chemical sensor. Polymer-analyte interactions change the index of refraction causing the propagating light velocity to change in a direction opposite to that of the index change. To measure this change, a reference propagating beam, adjacent to the sensing beam, is optically combined with the sensing beam creating an interference pattern of alternating dark and light fringes. When chemical or physical changes occur in the sensing arm, the interference pattern shifts. Real-time Fourier transform signal processing converts the time-dependent pattern to total phase shift which, is a measure of total analyte absorbed. Employing different polymer detection layers produces phase shifts whose pattern of response is used to identify and quantify the analytes present. Data taken from contaminated well sites measured using this interferometric sensor, and verified by independent laboratory measurements, is presented.
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Daniel P. Campbell, Daniel P. Campbell, David S. Gottfried, David S. Gottfried, Janet M. Cobb-Sullivan, Janet M. Cobb-Sullivan, } "Groundwater monitoring of VOCs with an interferometric optical waveguide sensor", Proc. SPIE 5586, Advanced Environmental, Chemical, and Biological Sensing Technologies II, (7 December 2004); doi: 10.1117/12.571391; https://doi.org/10.1117/12.571391
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