理论研究了氢分子离子在波长800 nm短周期啁啾脉冲方案下的高次谐波发射与孤立阿秒脉冲产生。经计算发现,当选取合适的啁啾参数时可以限制高次谐波同时由两核发射,从而减弱其空间的相互干涉,得到光滑连续且只有单核贡献的高次谐波谱平台区域。当啁啾参数β=6、激光脉冲半峰全宽τ₀=5 fs时,通过在单核贡献的连续谱上截取100阶谱线宽度合成了持续时间约为98 as的孤立阿秒脉冲。同时通过另一组参数计算也验证了当两核对高次谐波谱均有贡献时,不利于阿秒脉冲的产生。讨论中使用了经典的回碰动能图和时频分布图来解释高次谐波谱发射的物理机制。

High-order harmonics generation (HHG) and isolated attosecond pulse generation of H2+ in a few-cycle 800 nm chirped laser field are theoretically studied. Calculation results show that the HHG can limit the harmonics emitted by two nuclei at the same time through choosing the proper chirped parameters, which decreases the interference in the space and helps to obtain a smooth and continuous HHG flat supported only by single nucleus. An isolated 98 attosecond pulse is generated by synthesizing a spectrum width of 100 orders in the smooth and continuous region with the chirped parameters β=6 and the full width at half maximum τ0=5 fs. Calculation results also verify that when there are two nuclei contributing to the HHG, it is harmful to generate the isolated attosecond pulse. In the discussion, the classical returning energy maps and time frequency analysis are performed to explain the physical mechanism of HHG.