纯转动拉曼激光雷达中阶梯光栅单色仪设计

The Echelle Grating Monochromator's Design of Pure Rotational Raman Lidar

纯转动拉曼激光雷达测温系统通常根据大气中N2分子高低阶量子数的转动拉曼散射回波信号来反演大气温度,而探测转动拉曼谱的一种有效方法就是采用单色仪。文章阐述了中阶梯光栅单色仪的探测原理和结构,分析了探测谱线的高阶和低阶量子数及对应的拉曼散射波长。通过对中阶梯光栅的分光原理及色散能力分析计算了准直-聚焦系统的焦距,给出了光学系统的设计参数。利用Zemax软件对光路进行了模拟仿真,仿真结果表明:在探测激光波长为532nm的条件下,采用两块中阶梯光栅设计的单色仪,能够将529.05,530.40,533.77和535.13nm的拉曼谱线很好的分开,同时对对称量子数的谱线信号进行求和,增强系统的信噪比。中阶梯光栅单色仪体积较小,利于测温雷达系统的小型化。

The pure rotational Raman Lidar temperature measurement system usually retrieve atmospheric temperature according to the echo signal of high and low-level quantum numbers of N2 molecules. An effective method to detect the rotational Rarnan spectrum is taking a grating monochromator. In the present paper the detection principle and the structure of the echelle grating monochromator are described, the high order and lower order quantum number of the probe spectrum is resolved. The focal length of the collimating-focusing optical system is calculated by analyzing echelle grating＇s spectroscopic principle and dispersion ability. Subsequently spectral effect is simulated with Zemax software. The simulation result indicates that under the condition of the probe laser wavelength of 532 um and using echelle grating monochromator, Raman spectrums of 529.05, 530. 40, 533. 77, 535.13 nm can be separated well, at the same time, the SNR of the system is enhanced by summing the spectral signals of sym-metric quantum number. The echelle grating monochromator is small in size, and can easily meet the requirements of the minia-turization of Raman Lidar temperature measurement system.