At paraxial approximation the maximum of the matching function is increasing with increased divergence angle.For different brightness of pumping light, the optimum value of the angle is obtained.

• 发现在旁轴近似下，匹配函数的最大值随泵浦光发散角的增大而增大，在考虑到像散的影响后，得到泵浦光发散角的参考值。