Sub-ppt level detection of carbon monoxide and nitrous oxide enabled by mid-infrared doubly resonant photoacoustic spectroscopy
Qinxue Nie, Zhen Wang, Kun Duan, Mai Hu, Mengran Du, Wei Ren
Abstract
We report highly sensitive detection of carbon monoxide (CO) and nitrous oxide (N 2 O) using doubly resonant photoacoustic spectroscopy paired with a quantum cascade laser (QCL) at 4.57 μm. The butterfly-packaged QCL is used to exploit the CO absorption line at 2190.02 cm −1 and the N 2 O absorption line at 2191.42 cm −1 by scanning the injection current. Leveraging the simultaneous acoustic and optical resonances and adopting a lower photoacoustic detection frequency, we achieve a minimum detection limit of 0.85 part-per-trillion (ppt) for CO over the 500 s averaging time, and 0.7 ppt for N 2 O over the 200 s averaging time. Our approach demonstrates record sensitivity for CO and N 2 O detection compared to state-of-the-art optical gas sensors.