研究了不同能量的纳秒激光脉冲聚焦到单晶硅片上时, 激光等离子体的自由电子密度和温度以及损伤形貌随激光脉冲能量增加的变化规律。 研究结果表明： 激光脉冲击穿硅介质产生的激光等离子体的体积以及自由电子密度和温度大小, 决定了硅表面损伤的形貌特点和大小。 自由电子密度和温度的变化特点是： 随着激光脉冲能量的增加, 激光等离子体的体积不断增大, 自由电子温度缓慢增加而密度基本不变。 又由于激光等离子体的自由电子密度和温度呈现从中心到边缘由大到小的变化趋势, 所以损伤形貌总的特点是内部区域的熔化非常充分, 形成明显的周期性排列的规则条纹, 且条纹的排列趋势呈现环状； 中部区域熔化不充分, 形成条纹不很规则； 边缘区域处分界明显, 有时出现等离子体产生喷溅变色痕迹。

The free electron density and temperature of laser-induced plasma and the damage on the silicon surface were investigated. The results show that the volume and the free electron density of laser induced plasma, as well as the plasma temperature will determine the profile and the size of silicon superficial damage. It was also found that the volume of laser plasma will increase continuously and the temperature will increase slightly with the increase in the energy of laser pulse, while the density of free electrons will remain invariable. The free electron density and the temperature reduce gradually from centre to edge, so the damage appearance has the following features: The interior area of damage was melted so well that the periodic stripes were formed. The periodic stripes were quite irregular for the area not melted very well. The boundary of damage is apparent and sometimes color changes induced by plasma spattering were observed.