Integrated optical sensor for chemical analysis based on near-infrared evanescent wave absorbance measurements

Jochen Buerck; Joerg Mayer; Bernd Zimmermann; Hans-Joachim Ache

doi:10.1117/12.221737

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29 September 1995 Integrated optical sensor for chemical analysis based on near-infrared evanescent wave absorbance measurements

Jochen Buerck, Joerg Mayer, Bernd Zimmermann, Hans-Joachim Ache

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Proceedings Volume 2508, Chemical, Biochemical, and Environmental Fiber Sensors VII; (1995) https://doi.org/10.1117/12.221737
Event: European Symposium on Optics for Environmental and Public Safety, 1995, Munich, Germany

Abstract

Investigations into the optimization of a long-path integrated optical evanescent field absorbance sensor for the detection of nonpolar organic substances in water are described. The sensor is based on a multimode strip waveguide produced by Na⁺Ag⁺ ion- exchange in a borosilicate glass substrate and a hydrophobic silicone sensing layer deposited on the IO structure, that reversibly enriches organic contaminants from water or air. Light from a tungsten-halogen lamp in launched into the planar structure and evanescent wave absorption measurements of the organic species in the silicone superstrate are performed with a near-infrared diode array spectrograph. Polymethyl(phenyl)siloxanes with varying refractive index were prepared and tested as sensitive coating for the IO structure. The light transmission through the sensor may decrease up to 90% if the coated sensors come in contact with water. These losses caused by light scattering effects due to the formation of H₂O micro- emulsions in the silicone superstrate can be minimized by using polysiloxanes with a higher degree of cross-linkage. Measurements of aqueous trichloroethene samples were successfully performed in the region of the C-H first overtone vibration band. The sensitivity of the measurement can be raised distinctively by using polymethylphenylsiloxanes, which have a higher refractive index than polydimethylsiloxane. Kinetic experiments with aqueous trichloroethene samples showed a reversible sensor response with t₉₀ values in the range from 7-20 minutes.

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Jochen Buerck, Joerg Mayer, Bernd Zimmermann, and Hans-Joachim Ache "Integrated optical sensor for chemical analysis based on near-infrared evanescent wave absorbance measurements", Proc. SPIE 2508, Chemical, Biochemical, and Environmental Fiber Sensors VII, (29 September 1995); https://doi.org/10.1117/12.221737

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