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Proceedings Paper

PPLN laser-based system for chemical imaging
Author(s): Peter D. Ludowise; David K. Ottesen; Thomas J. Kulp; Uta-Barbara Goers; Mathias C. Celina; Karla Armstrong; Sarah W. Allendorf
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Paper Abstract

An infrared-imaging instrument is being developed to provide in situ qualitative and quantitative assessment of hydrocarbon contaminants on metallic surfaces for cleaning verification. A continuous-wave infrared optical parametric oscillator (OPO), based on the quasi-phasematched material periodically poled lithium niobate (PPLN), is interfaced with an InSb focal plane array camera to perform fast, non-invasive analysis by reflectance spectroscopy. The period range of the designed fan-out PPLN crystal determines the range of the output wavelength of the light source. It is able to scan hundreds of wavenumbers positioned in the range of 2820 - 3250 cm-1, which is sufficient to detect functional groups of common organic compounds (-CH, -OH, and -NH). The capability of the instrument has been demonstrated in a preliminary investigation of reflectance measurements for hydrocarbon solvents (methanol and d-limonene) on an aluminum surface. A substantial difference in absorption is obtained for the two solvents at two different laser-illumination wavelengths, thus permitting hydrocarbon detection and molecular species differentiation. Preliminary reflectance spectra of a mixture of aliphatic hydrocarbon lubricants and drawing agents on an aluminum panel are also presented. The relative thickness of the hydrocarbon thin film is determined by the intensity ratio of images acquired at two different laser illumination frequencies.

Paper Details

Date Published: 27 October 1999
PDF: 10 pages
Proc. SPIE 3753, Imaging Spectrometry V, (27 October 1999); doi: 10.1117/12.366314
Show Author Affiliations
Peter D. Ludowise, Sandia National Labs. (United States)
David K. Ottesen, Sandia National Labs. (United States)
Thomas J. Kulp, Sandia National Labs. (United States)
Uta-Barbara Goers, Sandia National Labs. (United States)
Mathias C. Celina, Sandia National Labs. (United States)
Karla Armstrong, Sandia National Labs. (United States)
Sarah W. Allendorf, Sandia National Labs. (United States)

Published in SPIE Proceedings Vol. 3753:
Imaging Spectrometry V
Michael R. Descour; Sylvia S. Shen, Editor(s)

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