气体自发拉曼系统激光脉冲外整形光路

设计了一种多级光学环腔串联的激光脉冲外整形光路。在气体自发拉曼散射激发系统中,有效地避免了在强激光脉冲功率密度条件下所造成的气体裂解、石英玻璃窗口损坏及可燃气体点燃等现象的发生,可大幅度提高弱的气体拉曼信号的信噪比。通过数值模拟优化设计,第一腔的延迟时间为原始激光的脉宽半高宽(FWHM),各腔间的延迟时间比是2的倍数,分束镜的分束比为30%～50%。使用两个光学环腔,可以将脉宽为6.5ns、能量为400mJ原激光展宽整形到35ns,激光峰值功率降低了20%左右,并小于0.02GW。在混合气体样池中完成了基于激光拉曼光谱定量的浓度测量。该技术可进一步应用在光学发动机中混合气浓度和温度场的定量测定。

Laser pulse beam external reshaping optical path used by gas spontaneous Raman spectrum excited system

A nanosecond-long laser pulse beam external reshaping optical path was designed using a series of multiple optical ring-cavities.In gas laser spontaneous Raman scattering experiments,it avoids effectively the strong laser induced gas dissociation,optical quertz window components damage and the ignition of the flammable gas,so improves substantially the signal-to-noise ratio of the weak signal generated by the Raman effect.The results of numerical study and optimization design showed that the delay time of the cavity 1 equals to the full-width-half-maximum(FWHM) of the original laser beam,and the ratios between the delay times of the subsequent cavities should be the nultiples of 2,the splitting ratio of the beam splitter is 30%~50%.Using 2 optical ring-cavities,the original laser beam with pulse width(FWHM) 6.5 ns,energy 400 mJ was widened to 35 ns(FWHM) with a peak power reduction of 20% to less than 0.02 GW.The concentration measurements were performed in the gas mixture pool based on the quantification by the laser Raman spectrum.This technique can be further used in the quantitative measurement of gas mixture concentration and temperature field of the optical engine.