飞秒激光诱导硅表面高频周期结构

High frequency femtosecond laser induced periodic spatial structure on silicon surface

通过引入双温方程电子数密度模型,德鲁德模型和波纹间隔理论Λ=λ/2n軌,得到高频波纹周期具有波长依赖性的特点,分析了在辐射光通量接近损伤阈值时,高频周期波纹在一定范围内接近λ/6~λ/4,且随入射激光通量近似成正比。同时基于时域有限差分法(FDTD)的方法对飞秒激光辐照硅表面电场分布进行数值仿真,在初始脉冲形成近波长波纹的情况下,硅表面的电场再分布使得激光能量大多沉积在凹槽边缘,产生高频周期性结构。在此基础上对初始凹槽深度和激发态下硅表面的光学性质(介电常数)进行分析,得到了形成高频周期波纹的条件。该研究对于理解飞秒激光造成硅表面形成周期结构及其在加工硅材料领域具有重要的参考意义。

By introducing the electron density model of the two-temperature equation, the Drude model and the theory of Λ=λ/2？, it was found that the high frequency ripple period had the characteristics of wavelength dependence. It was analyzed that the high frequency period ripple was close to λ/4-λ/6 in a certain range and was proportional to the incident laser fluence when the radiated light flux was close to the damage threshold. Besides, the electric field distribution on silicon surface irradiated by femtosecond laser was numerically simulated by FDTD method. The ripples formed by initial laser pulse on the silicon surface make most laser energy deposit on the edge of the groove, finally causing the generation of high-frequency periodic structure. What＇s more, through analyzing the initial groove depth and the optical properties （dielectric constant） of the excited silicon surface, the conditions for forming high-frequency periodic ripples were obtained. With the increase of dielectric constant which can be also expressed by the laser flunece, the surface morphology become more obvious. This study is of great significance for understanding the formation of high spatial frequency periodic structure of silicon surface caused by femtosecond laser and its application in the field of silicon materials processing.