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Sensors 2013, 13(3), 3331-3340; doi:10.3390/s130303331
Article

THz QCL-Based Cryogen-Free Spectrometer for in Situ Trace Gas Sensing

1,* , 1
,
2
,
2
,
1,3
 and
1
1 CNR, Istituto Nazionale di Ottica and LENS (European Laboratory for Non-linear Spectroscopy), Via Carrara 1, Sesto Fiorentino (FI) 50019, Italy 2 Cavendish Laboratory, University of Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK 3 NEST, CNR, Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa 56127, Italy
* Author to whom correspondence should be addressed.
Received: 3 January 2013 / Revised: 2 March 2013 / Accepted: 8 March 2013 / Published: 11 March 2013
(This article belongs to the Special Issue Laser Sensing and Imaging)
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Abstract

We report on a set of high-sensitivity terahertz spectroscopy experiments making use of QCLs to detect rotational molecular transitions in the far-infrared. We demonstrate that using a compact and transportable cryogen-free setup, based on a quantum cascade laser in a closed-cycle Stirling cryostat, and pyroelectric detectors, a considerable improvement in sensitivity can be obtained by implementing a wavelength modulation spectroscopy technique. Indeed, we show that the sensitivity of methanol vapour detection can be improved by a factor ≈ 4 with respect to standard direct absorption approaches, offering perspectives for high sensitivity detection of a number of chemical compounds across the far-infrared spectral range.
Keywords: terahertz spectroscopy; quantum cascade lasers; trace gas sensing terahertz spectroscopy; quantum cascade lasers; trace gas sensing
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Consolino, L.; Bartalini, S.; Beere, H.E.; Ritchie, D.A.; Vitiello, M.S.; De Natale, P. THz QCL-Based Cryogen-Free Spectrometer for in Situ Trace Gas Sensing. Sensors 2013, 13, 3331-3340.

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