Compact quantum cascade laser based quartz-enhanced photoacoustic spectroscopy sensor system for detection of carbon disulfide.

A compact gas sensor system based on quartz-enhanced photoacoustic spectroscopy (QEPAS) employing a continuous wave (CW) distributed feedback quantum cascade laser (DFB-QCL) operating at 4.59 µm was developed for detection of carbon disulfide (CS₂) in air at trace concentration. The influence of water vapor on monitored QEPAS signal was investigated to enable compensation of this dependence by independent moisture sensing. A 1 σ limit of detection of 28 parts per billion by volume (ppbv) for a 1 s lock-in amplifier time constant was obtained for the CS₂ line centered at 2178.69 cm^-1 when the gas sample was moisturized with 2.3 vol% H₂O. The work reports the suitability of the system for monitoring CS₂ with high selectivity and sensitivity, as well as low sample gas volume requirements and fast sensor response for applications such as workplace air and process monitoring at industry.