Three-dimensional spatio-temporal variation characteristics of pulse intensity is numerically simulated in detail in multi-pass amplifier of high power laser system. Theoretical calculation indicates that the complicated spatio-temporal distortion occurs as the pulse with specific spatio-temporal distribution passes the amplifier. This change imposes some difficulties on shaping prediction of the pulse power. The curve fitting method of input-output integral energy is proposed to achieve the inverse prediction of inject pulse shape formulti-pass amplifier system with high precision. The better prediction result is achieved not only for square pulse shape but also for multiple-steps complex pulse output, the relative power deviation reaches up to 0.032% for the square pulse output, and 0.78% for multiple-steps complex pulse output. In addition, the inverse prediction of more complicated Haan pulse is achieved. The relative power deviation is 0.13%. This method has not only high precision but also rapid computation and strong applicability.

对高功率激光多程放大系统中脉冲强度的三维时空变化特性进行了详细的数值分析，理论计算表明具有一定时空分布的光束在放大过程中会产生复杂的时空演化畸变，给脉冲功率的整形预测带来了一定的难度。提出了输入输出积分能量曲线拟合的方法，实现对多程放大系统输入脉冲波形的高精度反演预测，对于方波和复杂多台阶波形输出都能得到很好的预测结果，方波预测相对功率偏差低于0.032%，三台阶脉冲相对功率偏差为0.78%，另外还实现了更为复杂Haan脉冲的反演预测，相对功率偏差为0.13%。该方法不仅精度高，而且计算快速、适用性很强。