纯转动拉曼测温激光雷达中采用双光栅单色仪结构的优点是能提供优于10-7抑制比, 能够很好地抑制瑞利-米氏散射, 得到纯度很高的转动拉曼谱, 并且能够提高光的透射率, 具有长期稳定性, 但双光栅单色仪的光路结构复杂一直是系统中的难点。首先对两种光栅光路结构进行讨论, 得出光纤对称式光栅光路结构对于光栅效率的利用要优于光纤直线排列式光路结构, 并通过对光栅公式和转动拉曼光谱公式结合, 推导出光栅闪耀级次和衍射角关系方程。当光栅常数为600 line/mm时, 其第5级为最佳闪耀级次。

The double grating monochromator for a pure rotational Raman-lidar can provide for better than 10-7 suppression of the spectral line due to unshifted Mie+Rayleigh scattering, obtain high-purity rotational Raman spectrum, and improve transmission and stability of the optical system. The complexly structure of the double grating monochromator is always difficulty to Raman-lidar. Two optical paths of grating are compared and a conclusion can be drawn that the structure of beam path of grating of symmetrical arrange of optical fibre is better in grating efficiency than the structure of beam path of grating of linear arrange of optical fiber. Then a formula about relative of range of diffractive angle and order of grating is obtained through grating equation and rotational Raman equation. When grating constant is 600 line/mm, the fifth order of grating is optimal.