title: THz quartz-enhanced photoacoustic sensor for H₂S trace gas detection.
abstract: We report on a quartz-enhanced photoacoustic (QEPAS) gas sensing system for hydrogen sulphide (H₂S) detection. The system architecture is based on a custom quartz tuning fork (QTF) optoacoustic transducer with a novel geometry and a quantum cascade laser (QCL) emitting 1.1 mW at a frequency of 2.913 THz. The QTF operated on the first flexion resonance frequency of 2871 Hz, with a quality factor Q = 17,900 at 20 Torr. The tuning range of the available QCL allowed the excitation of a H₂S rotational absorption line with a line-strength as small as S = 1.13·10⁻²² cm/mol. The measured detection sensitivity is 30 ppm in 3 seconds and 13 ppm for a 30 seconds integration time, which corresponds to a minimum detectable absorption coefficient α(min) = 2.3·10⁻⁷ cm⁻¹ and a normalized noise-equivalent absorption NNEA = 4.4·10⁻¹⁰ W·cm⁻¹·Hz(-1/2), several times lower than the values previously reported for near-IR and mid-IR H₂S QEPAS sensors.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Spagnolo
authors.forename: Pietro
authors.initials: P
authors.lastname: Patimisco
authors.forename: Riccardo
authors.initials: R
authors.lastname: Pennetta
authors.forename: Angelo
authors.initials: A
authors.lastname: Sampaolo
authors.forename: Gaetano
authors.initials: G
authors.lastname: Scamarcio
authors.forename: Miriam S
authors.initials: MS
authors.lastname: Vitiello
authors.forename: Frank K
authors.initials: FK
authors.lastname: Tittel