Combined action of the bound-electron nonlinearity and the tunnel-ionization current in low-order harmonic generation in noble gases.
Combined action of the bound-electron nonlinearity and the tunnel-ionization current in low-order harmonic generation in noble gases.
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DOI：
10.1364/oe.21.025582
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发表时间：
2013-10
期刊：
影响因子：
3.8
通讯作者：
U. Sapaev;A. Husakou;J. Herrmann
中科院分区：
文献类型：
--
作者：
U. Sapaev;A. Husakou;J. Herrmann
本文从数值上研究了强飞秒激光脉冲在隧穿电离条件下抽运稀有气体的低次谐波产生。我们分析了由产生的等离子体引起的相位错配对这一过程的影响，并研究了由束缚电子非线性或隧道电离电流引起的谐波产生的来源与泵浦强度的关系。结果表明，在氩气中，当泵浦强度约为100 TW/cm²时，效率最高，其中低阶谐波主要来自束缚电子的三阶和五阶磁化率，而当泵浦强度大于300 TW/cm²时，隧道电离电流起主导作用。此外，我们预测用400 nm的泵浦脉冲可以产生相对较高的效率约为1.5 × 10⁻³的133 nm的VUV脉冲。
We study numerically low-order harmonic generation in noble gases pumped by intense femtosecond laser pulses in the tunneling ionization regime. We analyze the influence of the phase-mismatching on this process, caused by the generated plasma, and study in dependence on the pump intensity the origin of harmonic generation arising either from the bound-electron nonlinearity or the tunnel-ionization current. It is shown that in argon the optimum pump intensity of about 100 TW/cm² leads to the maximum efficiency, where the main contribution to low-order harmonics originates from the bound-electron third and fifth order susceptibilities, while for intensities higher than 300 TW/cm² the tunnel-ionization current plays the dominant role. Besides, we predict that VUV pulses at 133 nm can be generated with relatively high efficiency of about 1.5 × 10⁻³ by 400 nm pump pulses.