Telecom-grade fiber laser-based difference-frequency generation and ppb-level detection of benzene vapor in air around 3 μm |
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Authors: | J Cousin W Chen D Bigourd M Fourmentin and S Kassi |
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Abstract: | We report on the development of a field deployable compact laser instrument tunable over ∼232 cm−1 from 3.16 to 3.41 μm (2932.5–3164.5 cm−1) for chemical species monitoring at the ppb-level. The laser instrument is based on widely tunable continuous-wave difference-frequency
generation (DFG), pumped by two telecom-grade fiber lasers. DFG power of ∼0.3 mW near 3.3 μm with a spectral purity of ∼3.3
MHz was achieved by using moderate pumping powers: 408 mW at 1062 nm and 636 mW at 1570 nm. Spectroscopic performance of the
developed DFG-based instrument was evaluated with direct absorption spectra of ethylene at 3.23 μm (∼3094.31 cm−1). Absorption spectra of vapor-phase benzene near 3.28 μm (∼3043.82 cm−1) were recorded with Doppler-limited resolution. Line intensities of the most intense absorption lines of the ν
12 band near 3043.8 cm−1 were determined to support development of sensitive mid-infrared trace gas detection of benzene vapor in the atmosphere.
Detection of benzene vapor in air at different concentration levels has been performed for the first time using multi-pass
cell enhanced direct absorption spectroscopy at ∼3.28 μm with a minimum detectable concentration of 50 ppb (1σ). |
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