以分步离散傅里叶变换和四阶R－K法为基础，给出了解决激光三次谐波转换逆问题(即已知输出三倍频光场分布以及三次谐波转换器参数的情况下，求解输入基频光场分布)的方法，对三次谐波转换的逆问题进行了数值计算和分析，并讨论了逆算的初始光场条件对迭代计算次数及计算精度的影响。结果表明，对于设定的输出三倍频光场分布，可通过逆解三次谐波转换过程及数值迭代方法，求得相应的输入基频光场分布。

Based on some numerical techniques such as split-step Fourier transformation,fourth-order Runge-Kutta and iteration method,the method for solving the inverse problem of monochromatic third-harmonic generation,i. e. the fundamental field is calculated from the given third-harmonic field,is proposed.The numerical calculation is performed and analyzed. The effects of the initial fields on the time and the precision of the iterative calculation are also discussed. It can be shown that our method is available and efficient.