少周期非均匀场下原子空间位置对高次谐波发射的影响

摘要

本文通过数值求解含时薛定谔方程,研究了少周期非均匀激光脉冲作用下氦原子选取不同的空间位置时高次谐波的发射情况.通过对原子在纳米结构空隙中心附近区域不同空间位置上的高次谐波发射情况的研究发现,非均匀激光场中,即使原子处在中心附近的很小的区域内,原子的空间位置也直接影响着高次谐波发射.随着空间内原子坐标的增大,高次谐波的截止得到扩展,且谐波平台区并非单向扩展,而是向两端同时的扩展.通过时频分析和半经典三步模型研究了高次谐波发射的物理机制,并对获得的物理现象给出合理的解释.%We investigate the effect of space position of atom on high-order harmonics of He atom in few-cycle spatially inhomogeneous laser fields by solving time-dependent Schrsdinger equation.The space position of atom has great effect on the high harmonic generation even the atom in a small area of the middle.With the increase of space position of atom,the cutoff of the harmonics can be extended remarkably and the plateau area extends to the low order and high order at the same time.We also investigate emission time of harmonics in terms of the time-frequency analysis and the semi-classical three-step model to illustrate the physical mechanism of high-order harmonic generation.