中文摘要：

从非线性Schrodinger方程出发，根据线性的近似分析方法，通过把介质片厚度和片间空气间隔转化为线性与非线性传输距离比讨论了系统B积分值和空气间隔对非线性增益谱的影响。着重分析了激光介质片数以及B积分值和非线性增长率之间的关系，并讨论了增长率随B积分值与片数的变化规律。其他参量不变的情况下，片间空气间隔的增大，使增益谱向长波方向移动，而介质片数则对增益谱的最高增益和谱线位置都有影响。同时，对这一现象做了无空气间隔的等效模拟。

英文摘要：

Using a linear stability analysis method, a linearizing model derived from the nonlinear schroedinger equation is used to analyze the influence of the air gap between slabs on small-scale selffocusing modulation growth in a slab amplifier of a high power laser facility. The quantitative relations between B-integral, the number of slabs, the ratio of air gag interval distance to the thickness of slab, and nonlinear modulation gain spectrum are given explicitly. It is found that as the gap distance increase, the nonlinear gain spectrum moved toward to long spatial wavelength region. The number of slabs also influence the maximum gain value and its spatial frequency. In addition, an approximate expression was given to show the air gap influence by using a gain spectrum without air gap but with an equivalent power and B-integral value.