脉冲堆积激光三倍频过程的逆问题

Inverse Problem of Frequency Tripling of Pulses Stacking Laser

针对三倍频过程的逆问题,即如何在给定三倍频脉冲形状及三倍频系统参数的前提下,通过逆算得到输入基频光脉冲形状,并采用脉冲堆积法来获得所需的基频光脉冲,提出了相应的计算模型和方法。以分步傅里叶变换和四阶龙格-库塔法为基础,通过数值拟合等方法,建立了三倍频光强与输入基频光强之间的定量关系。以预期输出三倍频光脉冲为具有特定形状的整形脉冲为例,通过逆算得到了相应的输入基频光脉冲波形。在此基础上,计算获得了脉冲堆积器的衰减系数、延时等控制参数。进而通过对基频光时间波形的整形,实现了所要求的三倍频激光脉冲输出。研究结果表明,该逆算方法具有原理简单、计算快速准确等优点,可为三倍频过程激光脉冲整形设计提供参考。

A method for solving the inverse problem of frequency tripling, i. e. , how to calculate the shape of the fundamental field （1ω）, and how to obtain the required 1ω pulse by pulses stacking method for a given shape of the third-harmonic field （3ω）, was proposed. Eased on some numerical techniques such as split step Fourier transform and fourth-order Runge -Kutta, the quantitative relation between the input 1ω intensity and the output 3ω intensity was obtained by curve fitting method. Taking the shaping pulse with a certain shape as the required output 3ω pulse, the corresponding shape of the 1ω pulse can be determined by the inverse calculation. Furthermore, the parameters of the pulse stacker, such as attenuation and time delay, etc, were worked out. Consequently, the temporal pulse shaping for 1ω pulse can been realized, leading to the realization of the required output 3 pulse. The results indicate that the inverse problem can be solved quickly and precisely with the method proposed in this paper, and this method is useful for pulse shaping of frequency tripling.