在短脉冲激光作用下薄膜的损伤机制

计算了不同材料的能带带隙、初始电子密度、激光波长和激光脉宽等参效对薄膜的抗激光损伤闭值的影响，研究了在不同脉冲宽度激光作用下多光子离化和雪崩离化两种损伤机制的竞争．结果表明，在以平均电子能量不变为特征的雪崩电离的建立期间，光电离速度影响初始电子的浓度，从而影响雪崩电离和光电离之间的竞争．激光脉冲的宽度越大，雪崩电离对电子发展的贡献越大，而多光子离化的贡献越小．

Mechanism of short pulse laser induced damage in dielectric films

When band gap energy of materials is larger than photon energy, the electronic number density can be described by the Forkker-Planck function. The combination of avalanche ionization and photo ionization mechanisms had been considered and it had been taken as laser induced damage mechanism of films. The damage threshold affected by band gap, initial electronic density, laser wavelength, and pulse width had been investigated. Evaluating results indicate that during the course of stable avalanche ionization establishment which is characterized by the invariable average electronic energy, the electronic number generated by photo ionization can evidently affect the competition between avalanche ionization mechanism and photo ionization mechanism. When laser pulse width increases, avalanche ionization contributes more and photo ionization contributes less to cause films damage.