驱动激光波长对超短脉冲与原子相互作用产生高次谐波发射的影响

Influence of driving-laser wavelength on emission of high-order harmonic wave generated by atoms irradiated by ultrashort laser pulse

通过数值求解含时薛定谔方程方案,理论研究了在有质动力能不变条件下,不同波长超短激光辐照原子产生的高次谐波发射.发现随着驱动激光波长的增加,谐波发射的强度降低且发射谱中出现新的峰值结构.通过谐波发射行为的时间频率分析,电子密度的含时演化以及本征态布居含时分析发现,谐波新的峰值产生根源是电子从激发态电离后返回母体离子产生的谐波发射与从基态电离产生的谐波发射之间的干涉.

With the numerical solution of the time-dependent Schrodinger equation,we theoretically investigate the high-order harmonic emissions generated by the atoms irradiated by the ultrashort lasers with different wavelengths but the same pondermotive energy.As the driving-laser wavelength increases,the intensity of the high-harmonic emission decreases.Comparing with the harmonic spectra of atoms driven by a 1000-nm-wavelength laser pulse,a new peak structure appears in the spectra of atoms driven by a 5000-nm-wavelength laser wavelength.It is shown by the time-frequency analysis of the harmonic emission,the time-dependent evolution of the electron density,and the time-dependent population analysis of the eigenstate,that the physical mechanism behind the new peak appearing in the harmonic spectra is the interference between the harmonic emission generated by the electrons ionized out of the excited atoms returning to the parent ions and the harmonic emissions resulting from the ground state ionization.