长脉冲强激光整束热晕实验研究

WHOLE-BEAM THERMAL BLOOMING EXPERIMENTS WITH A LONG LASER PULSE

研究脉冲时间1.8ms,输出能量约200J,光束发散角2mrad的自由振荡钕玻璃光束,经2m焦距透镜聚焦后穿过充有0～0.6MPa氨的热晕池(热晕池长1m)产十的整束热晕效应。用CCD系统测量激光束腰直径的时间积分值随氨气压的变化曲线及束腰光强空间分布图象,用数字显示式能量计测量热晕吸收系数,用硅光二极管—数字采集,分析仪—Roland绘图仪—计算机处理系统,测量激光中心光强随时间的变化曲线。用KDP倍频—高速分幅相机系统记录激光场强分布随时间的畸变。并用解析理论计算值与实验结果进行了分析比较。

Whole -beam thermal blooming experiments have been done using a focused long pulse laser (τP= 1.8ms , E = 2001, angle spread θ = 2mrad ). A blooming cell is full of ammonia at 0 -6 atmosphere pressure. A CCD system is used to measure the diameter of the distorted laser beam waist and the intensity profile of the spot at waist. The absorption cofficients are measured by a digital calorimeter. The instantaneous irradiation intensity at spot centre is measured by a photodiode digital collector-Roland mapper-Computer system. The instantaneous intensity profile is measured by a high speed camera.