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Sensors 2016, 16(4), 439;

Improved Tuning Fork for Terahertz Quartz-Enhanced Photoacoustic Spectroscopy

Dipartimento Interateneo di Fisica, Università degli studi di Bari Aldo Moro e Politecnico di Bari, Via Amendola 173, Bari I-70126, Italy
Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA
NEST, CNR-Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, Pisa I-56127, Italy
Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
Author to whom correspondence should be addressed.
Academic Editor: Markus W. Sigrist
Received: 8 February 2016 / Revised: 14 March 2016 / Accepted: 23 March 2016 / Published: 25 March 2016
(This article belongs to the Special Issue Infrared and THz Sensing and Imaging)
Full-Text   |   PDF [2082 KB, uploaded 25 March 2016]   |  


We report on a quartz-enhanced photoacoustic (QEPAS) sensor for methanol (CH3OH) detection employing a novel quartz tuning fork (QTF), specifically designed to enhance the QEPAS sensing performance in the terahertz (THz) spectral range. A discussion of the QTF properties in terms of resonance frequency, quality factor and acousto-electric transduction efficiency as a function of prong sizes and spacing between the QTF prongs is presented. The QTF was employed in a QEPAS sensor system using a 3.93 THz quantum cascade laser as the excitation source in resonance with a CH3OH rotational absorption line located at 131.054 cm−1. A minimum detection limit of 160 ppb in 30 s integration time, corresponding to a normalized noise equivalent absorption NNEA = 3.75 × 10−11 cm−1W/Hz½, was achieved, representing a nearly one-order-of-magnitude improvement with respect to previous reports. View Full-Text
Keywords: quartz enhanced photoacoustic spectroscopy; quartz tuning fork; gas sensing; THz spectroscopy; quantum cascade laser quartz enhanced photoacoustic spectroscopy; quartz tuning fork; gas sensing; THz spectroscopy; quantum cascade laser

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Sampaolo, A.; Patimisco, P.; Giglio, M.; Vitiello, M.S.; Beere, H.E.; Ritchie, D.A.; Scamarcio, G.; Tittel, F.K.; Spagnolo, V. Improved Tuning Fork for Terahertz Quartz-Enhanced Photoacoustic Spectroscopy. Sensors 2016, 16, 439.

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