Wavelength selection and detection capability simulation of the mid-infrared DIAL for NO₂ detecion

Differential absorption lidar (DIAL) is an effective way to measure the concentration of nitrogen dioxide in extensive air with high precision. Based on the tunable solid-state laser absorption technique, the principle and systematic structure of differential absorption lidar were introduced. The absorption spectra of nitrogen dioxide in the range from 3.410 m to 3.435 m were measured with a step of 0.01 nm. The experimental results show that the correlation coefficient between the measured and the simulated absorption spectrum reaches to 92.01% at the standard condition (i.e., 1.0 atm, 25℃). Based on the analysis of measured absorption spectrum,the laser wavelength pair which includes the on-line 3.424 m and the off-line 3.414 m is determined. In addition, the signal pre-processing and denoising methods were studied. The simulation results show that the concentration errors of nitrogen dioxide can be less than 0.1 mg/m3 within 1 km by combining the signal pre-processing and the multiple autocorrelation.