Compact open-path detection of N2O gas with low concentration of ppb level based on QCL

Abstract

We measured nitrous oxide (N2O) gas at concentrations as low as 2ppb using a multi-pass gas cell (MPGC) with an path length of 10m. The quantum cascade laser (QCL) was spectrally scanned in the range of 4529.4nm–4531nm having the strongest linear absorption cross-section of 3.6710−18 cm2, where the spectral absorption region of CO and CO2 is avoided. The absorption levels at spectral lines of 4529.80nm and 4530.22nm were measured to demonstrate a relation with variation of concentration of N2O. This strategy could be used in low power of laser with a limit of power detector because we are using linear absorption phenomena.