A quartz enhanced photo-acoustic gas sensor based on a custom tuning fork and a terahertz quantum cascade laser

Year: 2014

Authors: Patimisco P., Borri S., Sampaolo A., Beere H. E., Ritchie D. A., Vitiello M., Scamarcio G., Spagnolo V.

Autors Affiliation: Dipartimento Interateneo di Fisica, Università e Politecnico di Bari, Via Amendola 173, I-70126 Bari, Italy;
IFN-CNR UOS Bari, via Amendola 173, 70126 Bari, Italy;
Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK;
NEST, CNR-Istituto Nanoscienze and Scuola Normale Superiore, Piazza San Silvestro 12, I-56127 Pisa, Italy

Abstract: An innovative quartz enhanced photoacoustic (QEPAS) gas sensing system operating in the THz spectral range and employing a custom quartz tuning fork (QTF) is described. The QTF dimensions are 3.3 cm × 0.4 cm × 0.8 cm, with the two prongs spaced by [similar]800 μm. To test our sensor we used a quantum cascade laser as the light source and selected a methanol rotational absorption line at 131.054 cm−1 ([similar]3.93 THz), with line-strength S = 4.28 × 10−21 cm mol−1. The sensor was operated at 10 Torr pressure on the first flexion QTF resonance frequency of 4245 Hz. The corresponding Q-factor was 74 760. Stepwise concentration measurements were performed to verify the linearity of the QEPAS signal as a function of the methanol concentration. The achieved sensitivity of the system is 7 parts per million in 4 seconds, corresponding to a QEPAS normalized noise-equivalent absorption of 2 × 10−10 W cm−1 Hz−1/2, comparable with the best result of mid-IR QEPAS systems.

Journal/Review: ANALYST

Volume: 139 (9)      Pages from: 2079  to: 2087

More Information: The authors acknowledge financial support from the Italian national projects: PON01_02238, PON02_00675 and PON02_00576. We thank A. Tredicucci for fruitful interactions, F. Tittel for helpful discussions, A. Kachanov for providing the custom quartz tuning fork and P. P. Calabrese for realizing the fork housing. M. S. V. acknowledge financial support of the Italian Ministry of Education, University, and Research (MIUR) through the program \”FIRB-Futuro in Ricerca 2010\” RBFR10LULP \”Fundamental research on terahertz photonic devices\”.
DOI: 10.1039/c3an01219k

Citations: 66
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