在纳秒级光脉冲多程放大研究中,Lowdermilk解析解仅考虑了增益完全恢复和完全不恢复两种极端情况.实际上,在脉冲间隔时间内放大器的增益恢复很可能介于完全恢复和完全不恢复之间.直接从速率方程出发,建立脉冲通量与激光上、下能级粒子数的相关方程,推导出上、下能级粒子数密度在脉冲与放大器发生相互作用时间间隔dT前后的递推关系,从而解决了增益不完全恢复问题.另外,把该模型的计算结果与Lowdermilk解析解和多程放大实验结果做了比较,分析了弛豫效应对能流放大特性的影响,并得到了比较准确、可靠的结果.

During the study on the multi-pass amplification of nanosecond light pulse, analytical results of Lowdermilk et al just care about two critical situations, namely, gain full-recovery and gain non-recovery. In fact, the gain recovery of amplifier during the pulse interval is most likely between those two recovery situations. In this paper, the equations about relationship between pulse fluence and population in the upper and lower energy level have been built up. Moreover, sequential relationship was deduced between time intervals during which light pulse interacts with population density in the upper and lower energy levels. Thus, the problem of gain non-recovery has been solved Moreover, the results calculated by this model were compared with those of Lowdermilk analysis model and multi-pass amplification experiment It was also analyzed that how the decay effect influenced on the characteristics of energy amplification· And relatively good and reliable results were achieved.