title: THz QCL-based cryogen-free spectrometer for in situ trace gas sensing.
abstract: We report on a set of high-sensitivity terahertz spectroscopy experiments making use of QCLs to detect rotational molecular transitions in the far-infrared. We demonstrate that using a compact and transportable cryogen-free setup, based on a quantum cascade laser in a closed-cycle Stirling cryostat, and pyroelectric detectors, a considerable improvement in sensitivity can be obtained by implementing a wavelength modulation spectroscopy technique. Indeed, we show that the sensitivity of methanol vapour detection can be improved by a factor ≈ 4 with respect to standard direct absorption approaches, offering perspectives for high sensitivity detection of a number of chemical compounds across the far-infrared spectral range.
authors.affiliation: CNR, Istituto Nazionale di Ottica and LENS (European Laboratory for Non-linear Spectroscopy), Sesto Fiorentino (FI) 50019, Italy. luigi.consolino@ino.it
authors.forename: Luigi
authors.initials: L
authors.lastname: Consolino
authors.forename: Saverio
authors.initials: S
authors.lastname: Bartalini
authors.forename: Harvey E
authors.initials: HE
authors.lastname: Beere
authors.forename: David A
authors.initials: DA
authors.lastname: Ritchie
authors.forename: Miriam Serena
authors.initials: MS
authors.lastname: Vitiello
authors.forename: Paolo
authors.initials: P
authors.lastname: De Natale
mesh_terms: D004867:Equipment Design; D005740:Gases / Q000302:isolation & purification*; D006801:Humans; D007259:Infrared Rays; D054023:Lasers, Semiconductor; D055068:Terahertz Spectroscopy
chemical_list: D005740:Gases