Mid-IR evanescent-wave absorption spectra of thin films and coatings measured with a ∼50-μm-thick planar Ge waveguide sensors

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

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Scopus citations

Abstract

We have fabricated IR-transmitting Ge waveguides as supported single crystals 30-100 μn 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 20x 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-μm thick waveguides, we demonstrate a clear increase in sensitivity to small samples with decreasing waveguide thickness.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsR.A. Lieberman
Pages371-377
Number of pages7
Volume3105
DOIs
StatePublished - 1997
Externally publishedYes
EventChemical, Biochemical and Environmental Fiber Senors IX - Munich, Germany
Duration: Jun 16 1997Jun 18 1997

Other

OtherChemical, Biochemical and Environmental Fiber Senors IX
CountryGermany
CityMunich
Period6/16/976/18/97

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Keywords

  • Attenuated total reflection
  • Chemical sensor
  • IR microscope
  • ZnS coating

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics

Cite this

Stone, J. J., Braiman, M. S., & Plunkett, S. E. (1997). Mid-IR evanescent-wave absorption spectra of thin films and coatings measured with a ∼50-μm-thick planar Ge waveguide sensors. In R. A. Lieberman (Ed.), Proceedings of SPIE - The International Society for Optical Engineering (Vol. 3105, pp. 371-377) https://doi.org/10.1117/12.276174