Mid infrared upconversion spectroscopy using diffuse reflectance

Nicolai Højer Sanders, Louis M. Kehlet, Jeppe Seidelin Dam, Peter Tidemand-Lichtenberg, Pablo Beato, Christian Pedersen

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


We present a novel approach for mid infrared (mid-IR) spectral analysis using upconversion technology applied in a diffuse reflectance setup. We demonstrate experimentally that mid-IR spectral features in the 2.6-4 μm range using different test samples (e.g. zeolites) can be obtained. The results are in good agreement with published data. We believe that the benefit of low noise upconversion methods combined with spectral analysis will provide an alternative approach to e.g. mid-IR Fourier Transform microscopy. We discuss in detail the experimental aspects of the proposed method. The upconversion unit consists of a PP:LN crystal situated as an intracavity component in a Nd:YVO 4 laser. Mixing incoming spectrally and spatially incoherent light from the test sample with the high power intracavity beam of the Nd:YVO 4 laser results in enhanced conversion efficiency. The upconverted light is spectrally located in the near infrared (NIR) wavelength region easily accessible for low noise Silicon CCD camera technology. Thus the room temperature upconversion unit and the Silicon CCD camera replaces noisy mid infrared detectors used in existing Fourier Transform Infrared Spectroscopy. We demonstrate specifically that upconversion methods can be deployed using a diffuse reflectance setup where the test sample is irradiated by a thermal light source, i.e. a globar. The diffuse reflectance geometry is particularly well suited when a transmission setup cannot be used. This situation may happen for highly scattering or absorbing samples.
Original languageEnglish
Title of host publicationProceedings of SPIE
Number of pages7
PublisherSPIE - International Society for Optical Engineering
Publication date2014
Publication statusPublished - 2014
SeriesProceedings of SPIE, the International Society for Optical Engineering


  • Infrared microscopy
  • Nonlinear frequency conversion
  • Diode lasers

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