Simulation of power-modulation mid-infrared integrated-path differential absorption lidar for probing benzene concentration

Aiming at the detection of benzene concentration in the atmosphere, a power-modulation scheme with laser wavenumber tuning is proposed in mid-infrared integrated-path differential absorption (IPDA) lidar. Based on the differential absorption lidar (DIAL) theory, we design the configuration of power-modulation IPDA lidar. Its central measurement and reference wavenumber are selected as 3090.3cm^-1 and 3137.7cm-1, and the power-modulation scheme of IPDA lidar is proposed through interband cascade laser (ICL) current-driving characteristic. The simulation model of power-modulation mid-infrared IPDA lidar is constructed, and then its theoretical analysis is carried out. Furthermore, the retrieval algorithm for benzene concentration is presented, and then the concentration precision as 1/f noise with different frequencies is analyzed with FFT retrievals of 1000. The detection performance of lidar such as signal-to-noise ratio (SNR) and relative error for path length and visibility is compared between direct current (DC) driving and altering current (AC) driving, i.e. power-modulation scheme. The results show that the uncertainty of concentration is consistent with the effect of 1/f noise, that the SNR increases with the increase of visibility or the decrease of path length and the relative error decreases with the increase of visibility or the decrease of path length, and that the SNR will increase with the increase in frequency, and the relative error will decrease under the same path length and visibility. Therefore, the power-modulation mid-infrared IPDA lidar can be more effective for probing benzene concentration.