Abstract

We report a portable broadband photoacoustic spectroscopic system for trace gas detection using distributed feedback quantum cascade laser arrays. By sequentially firing 128 lasers, our system acquires a photoacoustic spectrum covering ${565}\;{{\rm cm}^{- 1}}$ ($935{-}1500\;{{\rm cm}^{- 1}}$) with a normalized-noise-equivalent-absorption coefficient of ${2.5} \times {{10}^{- 9}}\;{{\rm cm}^{- 1}}\;{{\rm WHz}^{- 1/2}}$. The firing sequence that determines when and which laser to activate is programmable, which enables frequency-multiplexing excitation. For demonstration, 12 lasers are modulated simultaneously at distinct frequencies, and a photoacoustic spectrum is acquired within 13 ms. The compactness (${28\, {\rm cm}} \times {17\, {\rm cm}} \times {13\, {\rm cm}}$, 3.5 kg) and low power consumption enable convenient installation for on-site monitoring.

© 2020 Optical Society of America

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