High Repetition Rate Mid-Infrared Differential Absorption Lidar for Atmospheric Pollution Detection

Abstract

Developments in mid-infrared Differential Absorption Lidar (DIAL), for gas remote sensing, have received a significant amount of research in recent years. In this paper, a high repetition rate tunable mid-infrared DIAL, mounted on a mobile platform, has been built for long range remote detection of gas plumes. The lidar uses a solid-state tunable optical parametric oscillator laser, which can emit laser pulse with repetition rate of 500 Hz and between the band from 2.5 μm to 4 μm. A monitoring channel has been used to record the laser energy in real-time and correct signals. Convolution correction technology has also been incorporated to choose the laser wavelengths. Taking NO2 and SO2 as examples, lidar system calibration experiment and open field observation experiment have been carried out. The observation results show that the minimum detection sensitivity of NO2 and SO2 can reach 0.07 mg/m3, and 0.31 mg/m3, respectively. The effective temporal resolution can reach second level for the high repetition rate of the laser, which demonstrates that the system can be used for the real-time remote sensing of atmospheric pollution gas.

2 μm self-sweeping fiber laser oscillator for LIDAR applications

“…1. A key element of the scheme is a Tm-doped pulsed self-sweeping fiber laser (similar to the one presented in [5]). The self-sweeping range is up to 20 nm around 1.92 μm at sweeping rate of about 5 nm/s.…”

“…Gas-, fiber-based or solid-state lasers are usually used in this case [1][2][3]. Existing tunable lasers relying on complex and expensive tuning principles are often based on mechanically tuned spectral elements [4][5]. A fiber laser with self-induced frequency sweeping (selfsweeping laser) is not affected by this drawback.…”

Atmospheric carbon dioxide measurement from aircraft and comparison with OCO-2 and CarbonTracker model data

“…X H 2 O is the dry-air ratio of water vapour, "IWF" represents the integral weight function. IWF can be calculated using the temperature, pressure, and humidity profiles obtained by the AIMMS and the high-resolution transmission molecular absorption (HITRAN) database (Gordon et al, 2017). Zhu et al (2020) used the matched filter algorithm (MFA) to extract the weak echo signals over the ocean in previous research work.…”

Application of High-Speed Quantum Cascade Detectors for Mid-Infrared, Broadband, High-Resolution Spectroscopy

“…Its most prominent application is the detection and identification of gas-phase molecules, because significantly high sensitivity can be obtained by long-range propagation of a collimated beam in a gas. The atmospheric windows in the MIR enable environmental measurements in free space [ 17 , 18 ]. As multiple absorption lines of several gases can overlap in a specific spectral region, high-resolution, high-sensitivity broadband is always required in LAS.…”