An innovative quartz enhanced photoacoustic (QEPAS) gas sensing system operating in the THz spectral range and employing a custom quartz tuning fork (QTF) will be described. The QTF dimensions are 3.3 cm x 0.4 cm x 0.8 cm, with the two prongs spaced by ~ 800 μm. To test our sensor we used a quantum cascade laser as light source and selected a methanol rotational absorption line at 131.054 cm−1 (~3.93 THz), with line-strength S = 4.28•10-21 cm/mol. The sensor was operated at 10 Torr pressure on the first flexion QTF resonance frequency of 4245 Hz. The corresponding Q factor was 74760. 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.

Terahertz quartz enhanced photo-acoustic gas sensor employing a quantum cascade laser source

SPAGNOLO, Vincenzo Luigi;Patimisco P.;
2014

Abstract

An innovative quartz enhanced photoacoustic (QEPAS) gas sensing system operating in the THz spectral range and employing a custom quartz tuning fork (QTF) will be described. The QTF dimensions are 3.3 cm x 0.4 cm x 0.8 cm, with the two prongs spaced by ~ 800 μm. To test our sensor we used a quantum cascade laser as light source and selected a methanol rotational absorption line at 131.054 cm−1 (~3.93 THz), with line-strength S = 4.28•10-21 cm/mol. The sensor was operated at 10 Torr pressure on the first flexion QTF resonance frequency of 4245 Hz. The corresponding Q factor was 74760. 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.
4th EOS Topical Meeting on Terahertz Science & Technology
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11589/22752
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