Humidity enhanced N2O photoacoustic sensor with a 4.53 μm quantum cascade laser and Kalman filter

The 2.3% water vapor was added to the analyzed sample to improve the vibrational-translational (V-T) relaxation rate of N2O molecule transition, and therefore enhance the N2O photoacoustic signal. High performance with a minimum detection limit of 28 ppbv in 1 second and a measurement precision of 34 ppbv have been achieved, respectively.

Without sacrificing the time resolution of the system, the Kalman adaptive filtering improves the measurement precision of the system by 2.3 times. The ability of the N2O photoacoustic sensor was demonstrated by continuous measurement of atmospheric N2O concentration for a period of 7 hours.