紫外域波长选择对全天时水汽拉曼激光雷达探测性能的影响

Influence of Ultraviolet Wavelength Selection on Detection Performance of All-Day Water Vapor Raman Lidar

Nd∶YAG激光器三倍频输出的354.7nm光和四倍频输出的266.0nm光都位于紫外波段,都可作为水汽拉曼激光雷达的激励光源;从水汽拉曼激光雷达系统的实际建设出发,分别从后向散射系数、消光系数、大气透过率、臭氧吸收和太阳背景噪声等方面对激光雷达系统的探测性能进行分析,探讨354.7nm和266.0nm激光光源对拉曼激光雷达开展全天时大气水汽探测的影响。结果表明:在水汽探测中,266.0nm及其对应的氧气、氮气和水汽拉曼波长均位于日盲紫外区内,不受太阳背景噪声的影响,但会受到臭氧吸收的影响;354.7nm波段无臭氧吸收,但会受到太阳背景噪声的影响;在分光系统参数一致的情况下,激光雷达系统选用266.0nm波段激光光源时,白天水汽的有效探测距离为2.7km,选用354.7nm波段激光光源时,有效探测距离仅为0.6km;日盲紫外波长的选择可有效提高白天水汽拉曼激光雷达的探测距离,实现水汽的全天时探测。

The third and fourth harmonic outputs at 354.7nm and 266.0nm for Nd∶YAG pulsed laser are both within the ultraviolet wavelength band,and can be selected as the pump sources of a water vapor Raman lidar.Based on the practical construction of a water vapor Raman lidar system and from the aspects of backscattering coefficients,extinction coefficients,atmospheric transmissivity,ozone absorption and background noises,the detection performances of this lidar system are analyzed.The effects of the 354.7nm and 266.0nm laser sources on the daytime water vapor detection by this Raman lidar are investigated.The results show that the 266.0nm laser and its corresponding vibrational Raman wavelengths of oxygen,nitrogen,and water vapor are all within the blind ultraviolet region,not affected by the solar background noise but affected by the ozone absorption.At 354.7nm,there is no ozone absorption,but it is still influenced by the solar background noises.When the parameters for this wavelength selector system are kept the same,the effective detection range of daytime water vapor obtained by the designed Raman lidar is 2.7km when the 266.0nm is selected as the transmitter wavelength.In contrast,if354.7nm is selected,the effective detection range is only 0.6km.The solar blind ultraviolet wavelength selection can effectively increase the detection range of daytime water vapor by Raman lidar and ensure the realization of allday water vapor detection.