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基于动理论Vlasov-Poisson方程,建立了超短脉冲激光引起的SiO2材料表面库仑爆炸烧蚀机理的理论模型,计算了在多光子吸收与雪崩2种电离机制下材料中自由电子的非平衡态分布,并在此基础上定量分析了自洽电场导致的材料表面库仑爆炸的机理及激光参数对材料表面烧蚀的影响.结果表明,在飞秒激光作用下自由电子弛豫时间不是常数,而是与自由电子微观状态有关,表明弛豫时间近似模型在飞秒时间尺度下是不适用的.理论模型的烧蚀深度数值计算结果在0～1ps脉宽范围均与实验吻合得较好.
Based on the theory of Vlasov-Poisson equation, a theoretical model of Coulomb explosion ablation induced by ultrashort pulsed laser was established. The calculation of the non-equilibrium distribution of free electrons in the materials by multiphoton absorption and avalanche ionization Based on this, the mechanism of Coulomb explosion caused by self-consistent electric field and the influence of laser parameters on the ablation of the material surface were quantitatively analyzed.The results show that the relaxation time of free electron is not constant under the action of femtosecond laser, Which is related to the microscopic state of free electrons, indicating that the approximate model of relaxation time is not applicable on the femtosecond time scale.The numerical results of ablation depth of the theoretical model agree well with the experimental data at 0 ~ 1ps pulse width.