THz quartz-enhanced photoacoustic sensor employing a quantum cascade laser source
Authors: Spagnolo V., Patimisco P., Borri S., Sampaolo A., Scamarcio G., Vitiello M.S., Beere H.E., Ritchie D.A.
Autors Affiliation: Dipartimento Interateneo di Fisica, Università e Politecnico di Bari, CNR-IFN UOS BARI, Via Amendola 173, Bari, Italy; CNR-INO UOS Sesto Fiorentino, LENS, via N. Carrara 1, 50019 Sesto Fiorentino, Italy; NEST, Istituto Nanoscienze-CNR, Scuola Normale Superiore, Piazza San Silvestro 12, Pisa I-56127, Italy; Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
Abstract: We report on an innovative quartz enhanced photoacoustic (QEPAS) gas sensor operating in the THz spectral range, employing a custom quartz tuning fork (QTF) with the two prongs spaced by ~800 µm. To test our sensor we employed a quantum cascade laser light source and selected a methanol rotational absorption line falling at 131.054 cm-1 (~3.93 THz), with line-strength S = 4.28•10-21 cm. The sensor operated at 10 Torr pressure on the QTF first flexion resonance frequency at 4245 Hz. We achieved 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..
More Information: The authors acknowledge financial support from the Italian national projects: PON01_ 02238, PON02_ 00675 and PON02_ 00576. M. S. V. acknowledge financial support of the Italian Ministry of Education, University, and Research ( MIUR) through the program \” FIRB- Futuro in Rice rca 2010\” RBFR10LULP \” Fundamental research on terahertz photonic devices\”KeyWords: Chemical sensors; Gas detectors; Light sources; Nanophotonics; Photoacoustic spectroscopy; Quantum cascade lasers, Absorption lines; Gas sensing; Photoacoustic sensors; Quantum cascades; Quartz tuning fork; Quartz-enhanced photoacoustic spectroscopies; Resonance frequencies; Thz spectroscopy, QuartzDOI: 10.1117/12.2033620