氢气受激拉曼波长转换的研究.pdfVIP

摘 要 受激拉曼散射 （Stimulated Raman Scattering, SRS ）是一种三阶非线性效应，其最 大特点是经受激拉曼效应产生的激光具有波长的可调谐和相干特性，所以受激拉曼变 频有巨大的应用价值。本文以Nd:YAG 激光的基频和二倍频为泵浦光，研究了高压氢 气的一级Stokes 振动拉曼和转动拉曼的转换。 实验中完成了曲率半径为1 m 的Herriot 腔型1~17 次聚焦的实验。实验结果分析： 多次聚焦可以非常有效地降低受激拉曼的阈值。 本工作对比了曲率半径分别为1 m 和0.5 m 的Herriot 多程池实验，结果表明受激 拉曼的有效增益长度是影响受激拉曼的阈值和转换效率的决定性因素。 本文还研究了多次聚焦SRS 输出激光的脉冲能量稳定性及其光斑质量。实验结果 证明了多次聚焦的SRS 输出激光的稳定性要比单次聚焦的稳定性高，而且多次聚焦有 利于改善光斑质量。另外，对振动拉曼和转动拉曼级联变频做了初步的实验验证。 最后，本文提出两种新型的SRS 激光变频方案——腔内受激拉曼变频方案和缩束 受激拉曼变频方案。 关键词：受激拉曼散射(SRS) 一级Stokes Herriot 腔 转化效率 阈值 I ABSTRACT Stimulated Raman Scattering (SRS) is a process related with the third-order nonlinear effect. It is a very attractive technique in generating tunable and highly coherent radiation. The first-order Stokes of vibrational Raman and rotational Raman conversion in hydrogen gas pumped by the fundamental frequency and the second-harmonic of Nd:YAG laser were studied in this thesis, respectively. According to our experiments, it is observed that the SRS threshold is reduced significantly as the number of focus increased, when a multiple pass Herriot configuration is applied. Comparing the experimental data of Herriot cavities with mirrors of 1 m and 0.5 m radius of curvature, it is observed that the threshold of SRS and the conversion efficiency is strongly depend on the efficient length of the gain. In this thesis ，the stability of output pulse energy and the quality of laser spot of SRS in relationships with focus number were studied. Experimental results showed that the output pulse energy stability of multiple pass SRS is much better than that of single focus and the laser spot quality is improved significantly by the use of refocus. Furthermore, the cascade SRS of vibrational Raman an