为了增强高次谐波光谱强度, 提出了一种利用共振电离机制来提高谐波强度的方法。结果表明: 在 He 原子体系中, 受紫外共振电离影响, 谐波强度有 50 倍的增强。并且, 在啁啾场驱动下, 谐波截止能量也能增大, 进而获得一个高强度超宽谐波平台区。在 H2+ 分子体系中, 受电荷共振增强电离影响, 谐波强度也有近 20 倍的增强。并且在半周期单极场优化下, 该体系谐波截止能量也得到延伸, 进而获得一个只由单能量峰贡献的谐波平台区。进一步研究表明, 在两个体系的谐波平台区上选择一定的谐波叠加, 可分别获得脉宽在 36 as 和 32 as 的阿秒脉冲。初步的研究证实了所提出的方案有助于增强阿秒脉冲强度。

In order to enhance the intensity of high order harmonic spectrum, a method of improving harmonic intensity by using resonance ionization is proposed. The results show that, in case of He atom system, the harmonic intensity can be enhanced by 50 times under the influence of ultraviolet resonance ionization. Moreover, with the introduction of chirped pulse, the harmonic cutoff can also be extended, showing an intense and broad harmonic plateau. In case of H+2 molecule system, the harmonic intensity canbe enhanced by nearly 20 times under the influence of charge resonance enhanced ionization. And with the optimization of the half-cycle unipolar pulse, the extension of harmonic cutoff for H+2 molecule system can also be achieved, showing a harmonic plateau contributed by single harmonic emission peak. The further study shows that by superposing some harmonics on the harmonic plateaus, the attosecond pulses with durations of 36 as and 32 as can be obtained for the two systems, respectively. It is confirmed that the proposed scheme is helpful to enhance the intensity of attosecond pulse.