Generation of an extreme ultraviolet supercontinuum and isolated sub-50 as pulse in a two-colour laser field
Generation of an extreme ultraviolet supercontinuum and isolated sub-50 as pulse in a two-colour laser field
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DOI：
10.1088/0953-4075/42/12/125603
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发表时间：
2009-06
期刊：
影响因子：
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通讯作者：
Gangtai Zhang;Xue-shen Liu
中科院分区：
文献类型：
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作者：
Gangtai Zhang;Xue-shen Liu
从理论上研究了氦离子在由5 fs/800 nm激光脉冲和64 fs/2400 nm激光脉冲合成的双色激光场中的高次谐波产生。计算结果表明，当初始态为基态和第一激发态的相干叠加态时，谐波谱呈现出超宽的极紫外超连续谱.通过叠加一系列适当选择的谐波，获得了持续时间为47 As的孤立阿秒脉冲。与单色场中基态的情况相比，这种孤立的阿秒脉冲的强度高出六个数量级。我们还证明了这些结果的时频分析和半经典三步模型。
We theoretically study high-order harmonic generation when a helium ion is exposed to a two-colour laser field, which is synthesized by a 5 fs/800 nm laser pulse and a 64 fs/2400 nm laser pulse. Our numerical results show that the harmonic spectrum exhibits an ultrabroad extreme ultraviolet supercontinuum when the initial state is prepared as a coherent superposition of the ground state and the first excited state. By superposing a series of properly selected harmonics, an isolated attosecond pulse with a duration of 47 as is obtained. Compared with the case of the ground state in a one-colour field, the intensity of this isolated attosecond pulse is six orders of magnitude higher. We also demonstrate these results in terms of the time–frequency analysis and the semiclassical three-step model.