title: Quantum cascade laser-based photoacoustic sensor for trace detection of formaldehyde gas.
abstract: We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH(2)O) using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 μm. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm(-1) is selected for CH(2)O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters.
authors.affiliation: Dipartimento Interateneo di Fisica "M. Merlin", Università and Politecnico of Bari, and Laboratorio Regionale CNR-INFM "LIT3", Bari, I-70126, Italy; E-Mails:  cinzia.difranco@fisica.uniba.it  (C.-D.F.);  spagnolo@fisica.uniba.it  (V.S.);  lugara@fisica.uniba.it  (P.-M.L.);  scamarcio@fisica.uniba.it  (G.S.).
authors.forename: Angela
authors.initials: A
authors.lastname: Elia
authors.forename: Cinzia
authors.initials: C
authors.lastname: Di Franco
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Spagnolo
authors.forename: Pietro Mario
authors.initials: PM
authors.lastname: Lugarà
authors.forename: Gaetano
authors.initials: G
authors.lastname: Scamarcio