A portable N2O sensor based on quartz-enhanced photoacoustic spectroscopy with a distributed-feedback quantum cascade laser for medical and atmospheric applications

A portable sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) is reported to analyze trace gases. QEPAS is a high sensitivity and very compact well-established spectroscopic technique for sensitive and selective detection of trace gases. A distributed feedback quantum cascade laser (DFB-QCL) emitting at 4474 nm is utilized as excitation light source. N2O has been selected as the target molecule, in order to evaluate the performance of the sensor. By analyzing the QEPAS peak signal as a function of the N2O concentration, the response of the sensor has been investigated and a sensitivity of 0.24 mV/ppb and a linearity of 0.999 have been found. An Allan deviation analysis has been performed to determine the long-term performance of the sensor. A minimum detection limit of 2 ppb for 100 s integration time has been achieved. A precision and stability of 100 ppb (0.5 %) have been demonstrated as well