Two-tone frequency modulation spectroscopy for ambient-air trace gas detection using a portable difference-frequency source around 3 mu m

Year: 2006

Authors: Maddaloni P., Malara P., Gagliardi G., De Natale P.

Autors Affiliation: CNR – Istituto Nazionale di Ottica Applicata and European Laboratory for Non-Linear Spectroscopy, Comprensorio “A. Olivetti”, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy

Abstract: We report a portable, widely tunable, mW-power mid-infrared spectrometer based on difference-frequency generation in a periodically poled lithium-niobate crystal, realized in a compact and robust design. The analytical performance for real-time monitoring of natural-abundance trace gases in ambient air is evaluated, pointing out the possibility of field applications. In a direct-absorption scheme, a minimum detectable concentration of 3 ppb Hz(-1/2) is demonstrated around 3.3 mu m for methane at atmospheric pressure. The sensitivity is further improved by using a two-tone frequency modulation spectroscopy technique that provides an enhancement of a factor of 100 in the signal-to-noise ratio, thus yielding a minimum absorption coefficient of 5.3×10(-9) cm(-1) Hz(-1/2).


Volume: 85 (2-3)      Pages from: 219  to: 222

KeyWords: Absorption; Air; Atmospheric pressure; Crystals; Gases; Lithium niobate; Methane; Signal to noise ratio; Spectroscopic analysis; Trace analysis, Absorption coefficient; Frequency modulation spectroscopy technique; Real-time monitoring; Trace gases, Infrared spectrometers
DOI: 10.1007/s00340-006-2299-6

Citations: 27
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