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Infrared spectroscopy based on broadly tunable quantum cascade lasers and polycrystalline diamond waveguides

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Abstract

Recently emerging broadly tunable quantum cascade lasers (tQCL) emitting in the mid-infrared (MIR) are a versatile alternative to well established thermal emitters in combination with interferometers as applied in Fourier transform infrared (FTIR) spectroscopy. The wide and highly spectrally resolved wavelength tuning characteristics along with superior spectral energy density renders laser-based vibrational spectroscopy methods an efficient alternative vs. conventional molecular spectroscopies. Using diamond in attenuated total reflection (ATR) sensing formats benefits from the physical robustness and chemical resistivity of the internal reflective element (IRE) material. While inherent material absorption frequently limits the optical path length within diamond ATR elements, the herein presented design combining bright tQCLs with a multi-reflection polycrystalline diamond (PCD) ATR element enables an optical beam path length of approximately 5 cm. Thereby, sensitive spectroscopic measurements in the MIR are enabled. As an example, non-invasive glucose monitoring in human saliva is examined, highlighting the potential benefits of the proposed analytical concept with regards to exquisite sensitivity and selectivity in combination with a robust sensing interface, i.e., diamond. This approach paves the way towards directly analyzing molecular constituents in complex and potentially corrosive biomedical and biochemical matrices.

Graphical abstract: Infrared spectroscopy based on broadly tunable quantum cascade lasers and polycrystalline diamond waveguides

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Publication details

The article was received on 17 May 2018, accepted on 19 Jul 2018 and first published on 14 Aug 2018


Article type: Paper
DOI: 10.1039/C8AN00919H
Citation: Analyst, 2018, Advance Article
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    Infrared spectroscopy based on broadly tunable quantum cascade lasers and polycrystalline diamond waveguides

    J. Haas, E. V. Catalán, P. Piron, M. Karlsson and B. Mizaikoff, Analyst, 2018, Advance Article , DOI: 10.1039/C8AN00919H

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