Advance of ground based differential absorption lidar at 0.94 μm

In order to better detect the vertical profile of the tropospheric atmospheric water vapor, some improvements have been made to the established 935 nm differential absorption lidar. Taking the dual-channel receiving measure, the near-field channel telescope is also a beam expander that emitted laser light. The polarizing beamsplitter and quarter wave plate were used to isolate emitted light and echoed light in near-field channel, cassegrain telescope was applied in the far-field channel(main channel), thereby the near-ground dead zone of the lidar was reduced. The wavelength was shifted to 936.0-936.5 nm. The power of seed laser and the purity of the emission spectrum was increased, thereby the detection accuracy was improved. The detection span range was extended from 600-2 000 m to 250-3 000 m, and the random error was 5%.