【摘要】 建立了一种纳秒级多腔式激光脉冲扩展系统。通过激光脉冲展宽,该系统可以有效降低脉冲激光的峰值功率,从而在激光燃烧诊断实验中避免激光诱导等离子体的产生,减少背景干扰,有效提高信噪比。建立了理论模型,对影响脉冲展宽的分束比、腔长以及光学腔个数等几个主要参数进行了分析,并通过数值计算实现了各参数的优化。利用建立的多腔串联式激光脉冲展宽器,对Nd∶YAG脉冲激光器二倍频激光进行了脉冲展宽,将脉宽为7.8 ns的脉冲激光分别展宽为17,35和72 ns,激光的峰值功率最大可降低为原激光峰值功率的9%左右,并保持了较好的光束质量。将该展宽器应用于自发喇曼散射实验中,很好地解决了激光诱导击穿光谱对喇曼信号的干扰,取得了较好的实验结果。更多还原

【Abstract】 A multi-cavity passive nanosecond laser pulse stretching system was designed.The system could reduce laser peak powers and avoid the laser induced plasma spark,so that it reduces background interference and improves the signal to noise ratio in combustion diagnostics.The theoretical model of the pulse-stretching process for an arbitrary number of optical ring cavities was introduced,and several key parameters that affect on pulse width,beam-splitter reflectivity,cavity length and total number of optical cavities were analyzed.Finally,the designed multi-cavity laser pulse stretcher was used in broadening the Nd:YAG laser harmonic pulse width.Results indicate that a 7.8 ns input laser pulse has been converted into approximately the output laser pulses in 17 ns,35 ns and 72 ns,respectively.Furthermore,the laser peak power has been reduced to 9% of the original laser peak power,meanwhile,it maintains the good beam quality.The stretcher was also used in the spontaneous Raman scattering experiments,and results show it well resolves the laser induced breakdown spectroscopy of the Raman signal and achieves good results.更多还原