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Proceedings Paper

Mid-IR evanescent-wave absorption spectra of thin films and coatings measured with a ~50-um-thick planar Ge waveguide sensor
Author(s): James J. Stone; Mark S. Braiman; Susan E. Plunkett
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Paper Abstract

We have fabricated IR-transmitting Ge waveguides as supported single crystals 30 - 100 micrometers in thickness. These waveguides are useful as internal reflection elements for evanescent-wave absorption sensing and spectroscopy, when used in conjunction with a Fourier transform infrared microscope. This combination affords great sensitivity to small numbers of IR-absorbing molecules near the waveguide surface, and is especially useful for analyzing thin coatings on small-area substrates. For example, we have selectively observed absorption bands, as high as 20 times the noise level, from the adhesive layer of a 0.07 mm2 piece of Scotch tape without observing absorption from the backing. By comparing spectra taken using 70- and 30-micrometer thick waveguides, we demonstrate a clear increase in sensitivity to small samples with decreasing waveguide thickness.

Paper Details

Date Published: 30 May 1997
PDF: 7 pages
Proc. SPIE 3105, Chemical, Biochemical and Environmental Fiber Sensors IX, (30 May 1997); doi: 10.1117/12.276174
Show Author Affiliations
James J. Stone, Univ. of Virginia (United States)
Mark S. Braiman, Univ. of Virginia (United States)
Susan E. Plunkett, Univ. of Virginia (United States)

Published in SPIE Proceedings Vol. 3105:
Chemical, Biochemical and Environmental Fiber Sensors IX
Robert A. Lieberman, Editor(s)

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