Valavanis, Alexander and Chowdhury, Siddhant and Burnett, Andrew D. and Clarkson, Adam R. and Bacon, David R. and Khanna, Suraj P. and Davies, Alexander Giles and Linfield, Edmund H. and Dean, Paul (2016) Diffuse-Reflectance Spectroscopy Using a Frequency-Switchable Terahertz Quantum Cascade Laser. IEEE Transactions on Terahertz Science & Technology, 6 (2). 341 -347. ISSN 2156-342X

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We demonstrate diffuse-reflectance (DR) spectroscopy of powders using a discretely-tunable terahertz-frequency quantum cascade laser (THz QCL) with a heterogeneous active region. DR signatures were obtained at frequencies of 3.06, 3.21, 3.28, and 3.35 THz, and the relative absorption coefficients were inferred at each frequency using a Kubelka-Munk (KM) scattering model. The spectral lineshapes reproduce the absolute Beer-Lambert (BL) absorption spectra of a range of materials, which were also measured using conventional transmission-mode THz time-domain spectroscopy. It is shown that the DR technique works reliably for materials that include pharmaceutical compounds and foodstuffs, with BL absorption coefficients in the range 2-10 mm(-1). This method is potentially suitable for automated material identification, without any requirement for a priori knowledge of the refractive index or scattering properties of the sampled material.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s Institute of Electrical and Electronics Engineers.
Uncontrolled Keywords: Infrared spectra, quantum cascade lasers, spectroscopy, submillimeter-wave technology
Subjects: Engineering > Electronics and Electrical Engineering
Applied Physics/Condensed Matter
Depositing User: Dr. Rajpal Walke
Date Deposited: 17 Nov 2017 08:20
Last Modified: 17 Nov 2017 08:20

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