激光损伤过程中导带电子产生机理

The Mechanisms of Free Conduction-band Electron Generation during Laser Damage Process

价带电子跃迁至导带形成自由电子,长激光脉冲作用时,自由电子吸收能量并传给晶格,使材料温度升高;短激光脉冲作用时,自由电子发生碰撞离化,使导带中电子数目急剧上升,当材料达到一定温度或自由电子达到临界浓度时便发生损伤.随着激光技术的发展,人们不断的完善导带电子的产生机理,以达到计算值与实验结果相一致;激光脉冲越短,越多的光—电子相互作用机制会影响导带电子的产生,雪崩离化、多光子离化、导带电子衰减及导带电子能量分布等相互耦合,导带自由电子的产生过程非常复杂.文中综述了激光损伤过程中导带电子产生的机理模型,并提出了应用于亚皮秒及飞秒激光脉冲的耦合多速率方程.

Electrons will be excited from valence to conduction band during laser irradiation. For long pulse laser, the energy of free electrons will transfer to the lattices and the temperature will increase, but for short pulse laser, free electrons will initiate avalanche and makes the electron density increase greatly, when the temperature increase to melting point or the electrons increase to critical density, laser damage will occur. With the development of laser technology, numerous studies have been done to make the free electron generation mechanisms perfect to interpret experiment results. The shorter of the laser pulse, the generation mechanism of free electrons is more complex. For ultra short laser pulse, avalanche, multiphoton ionization, electron decay and the energy distribution are coupled together. We summarize the models of free electron generation during laser damage process. At the end, we develop a new free electron generation model and give the corresponding Coupled Multiple Rate Equation.