Remote sensing of atmospheric aerosol and gas using Scheimpflug lidar (SLidar) based on diode lasers

Abstract: Recently, a new lidar technique for atmospheric remote sensing based on Scheimpflug principle referred to as Scheimpflug lidar (SLidar) [1-3], was developed. When a laser beam is transmitted into the atmosphere, the implication of the Scheimpflug principle is that the backscattering echo of the entire illuminated probe volume can still be in focus simultaneously without diminishing the aperture, as long as the object plane (laser beam, or planeoffocus), image plane and the lens plane intersect with each other. The backscattering echo of the transmitted laser beam is then anglularly resolved by using a tilted line scan or two-dimensional CCD/CMOS camera satisfying the Scheimpflug principle Thus, continuous-wave (CW) light sources, such as diode lasers, can be employed for range-resolved remote sensing instead of using complicated nanosecond-scale pulsed light sources as in the cases of conventional lidar techniques. A robust and inexpensive SLidar system based on compact laser diodes and array detectors has been developed, which greatly reduces the system complexity and cost compared to conventional pulsed lidar techniques. A proof-of-principle demonstration of CW differential absorption lidar (CW-DIAL) based on the SLidar technique is presented. By utilizing a 30mW narrowband (10 MHz) CW laser diode emitting at around 760 nm, the detailed shape of an oxygen absorption line can be resolved remotely, and the range-resolved oxygen concentration can be retrieved as well. Further, continuous atmospheric aerosol monitoring with a 3.2W 808nm laser diode and an area CMOS sensor was also performed during daytime. The promising results demonstrated in the work show great potential for the SLidar technique for remote atmospheric aerosol and gas sensing, and renews hope for robust and realistic instrumentation for atmospheric lidar sensing.