Mid-IR evanescent-wave absorption spectra of thin films and coatings measured with a ~50-um-thick planar Ge waveguide sensor

James J. Stone; Mark S. Braiman; Susan E. Plunkett

doi:10.1117/12.276174

30 May 1997 Mid-IR evanescent-wave absorption spectra of thin films and coatings measured with a ~50-um-thick planar Ge waveguide sensor

James J. Stone, Mark S. Braiman, Susan E. Plunkett

Author Affiliations +

Proceedings Volume 3105, Chemical, Biochemical and Environmental Fiber Sensors IX; (1997) https://doi.org/10.1117/12.276174
Event: Environmental Sensing III, 1997, Munich, Germany

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.

Citation Download Citation

James J. Stone, Mark S. Braiman, and Susan E. Plunkett "Mid-IR evanescent-wave absorption spectra of thin films and coatings measured with a ~50-um-thick planar Ge waveguide sensor", Proc. SPIE 3105, Chemical, Biochemical and Environmental Fiber Sensors IX, (30 May 1997); https://doi.org/10.1117/12.276174

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