title: A quartz enhanced photo-acoustic gas sensor based on a custom tuning fork and a terahertz quantum cascade laser.
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 ∼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) (∼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.
authors.affiliation: Dipartimento Interateneo di Fisica, Università e Politecnico di Bari, Via Amendola 173, I-70126 Bari, Italy. v.spagnolo@poliba.it.
authors.forename: Pietro
authors.initials: P
authors.lastname: Patimisco
authors.forename: Simone
authors.initials: S
authors.lastname: Borri
authors.forename: Angelo
authors.initials: A
authors.lastname: Sampaolo
authors.forename: Harvey E
authors.initials: HE
authors.lastname: Beere
authors.forename: David A
authors.initials: DA
authors.lastname: Ritchie
authors.forename: Miriam S
authors.initials: MS
authors.lastname: Vitiello
authors.forename: Gaetano
authors.initials: G
authors.lastname: Scamarcio
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Spagnolo