飞秒激光烧蚀固体材料的过程及表面形貌研究

发布时间：2018-05-26 06:38

本文选题：飞秒激光 + 周期性结构　；参考：《山东师范大学》2015年硕士论文

【摘要】：飞秒激光脉冲由于快、微、强等特点，在细微加工领域表现出了得天独厚的优势。同时，飞秒激光与材料的相互作用过程是一个非常复杂的过程，对于不同材料，不同的激光能量，飞秒激光与材料作用的机理不同。本文对飞秒激光与材料的相互作用过程进行了理论与实验研究，我们做的具体工作如下：首先探讨了飞秒激光与材料相互作用的过程与机理，对双温方程进行简化，利用fortran软件进行有限元差分计算，模拟得出了不同入射激光功率密度下金属铜和钛的电子和晶格温度随时间的演化规律，并总结得出了金属铜和钛电子晶格能量耦合时间随入射激光功率密度的变化规律。其次研究了飞秒激光诱导金属表面的周期性结构随入射激光能量的演变情况，当入射激光能量较低，在材料的烧蚀阈值附近时，我们在烧蚀中心区域清楚的看到了垂直于入射激光极化方向的周期性表面结构。随着入射激光能量不断增加，位于烧蚀区域中心位置处的周期性条纹结构逐渐被破坏，在烧蚀区域的外围区域周期性条纹结构仍清晰可见，并用周期性结构出现的阈值理论解释了周期性结构外移出现的原因。在高能量激光入射下，烧蚀区域周期性表面结构进一步被破坏，不再清晰可见，在外围区域出现了纳米颗粒，但条纹结构的周期并未发生变化。我们通过比较实验测得的不同入射激光能量下金属铜和钛的周期性条纹结构的周期与用公式计算出的周期比较，理论与实验符合较好，得出结论：飞秒激光诱导周期性条纹结构的周期与入射激光能量无关，与金属种类有关。另外，我们还对半导体硅材料进行了烧蚀分析，发现了不同于金属材料的波纹状周期性结构。我们以钛为靶材，通过建立入射激光功率与烧蚀孔径之间的关系间接计算得到钛的单脉冲烧蚀阈值为0.20J/cm2。同时我们对飞秒激光烧蚀硅靶后不同烧蚀区域进行元素成分分析，得出随着脉冲个数的增加，烧蚀区域的氧含量也随之增加，对于相同脉冲个数，不同烧蚀区域的氧含量也不尽相同，烧蚀中心区域的氧含量要明显高于边缘区域，这对于以后的飞秒激光精细加工有着很好的指导作用。最后我们固定入射激光能量，，对不同入射激光脉冲个数下飞秒激光烧蚀金属铜和钛的烧蚀形貌与周期性结构产生的规律及原因作了简要分析，得到了烧蚀孔径与脉冲个数的变化关系：当入射激光脉冲个数比较少，烧蚀孔径随脉冲个数线性增加，当入射激光脉冲个数增大到400个时，烧蚀孔径随入射激光脉冲个数的影响不大。当入射激光的能量密度一定时，随着脉冲个数的增加，烧蚀区域的面积在逐渐增加，我们在烧蚀区域的边缘发现了明显的周期性结构，并从激光脉冲能量时空上的高斯分布特征和脉冲能量累积效应，讨论了脉冲个数对周期性波纹结构产生的影响。
[Abstract]:The femtosecond laser pulse has a unique advantage in the field of fine processing because of its characteristics such as fast, micro and strong. At the same time, the interaction process between femtosecond laser and material is very complicated. For different materials and different laser energy, the mechanism of femtosecond laser interacting with material is different. In this paper, the interaction between femtosecond laser and materials is studied theoretically and experimentally. Firstly, the process and mechanism of femtosecond laser interaction with materials are discussed. The two-temperature equation is simplified, and the finite element difference calculation is carried out by using fortran software. The evolution law of electron and lattice temperature of metal copper and titanium with time under different incident laser power density is obtained, and the variation of energy coupling time of metal copper and titanium electron lattice with incident laser power density is summarized. Secondly, the evolution of periodic structure of metal surface induced by femtosecond laser with incident laser energy is studied. The periodic surface structure perpendicular to the polarized direction of the incident laser is clearly observed in the ablation center. With the increasing of the incident laser energy, the periodic stripe structure at the center of the ablative region is destroyed gradually, and the periodic stripe structure is still visible in the peripheral region of the ablative region. The reason of the outward shift of periodic structure is explained by the threshold theory of periodic structure. The periodic surface structure of the ablative region is further destroyed under the high energy laser incident and is no longer clearly visible. Nanoparticles appear in the peripheral region, but the periodicity of the stripe structure does not change. By comparing the periodicity of the periodic stripe structures of copper and titanium at different incident laser energies measured experimentally with those calculated by the formula, the theoretical and experimental results are in good agreement. It is concluded that the periodicity of periodic stripe induced by femtosecond laser is independent of the energy of incident laser and is related to the type of metal. In addition, we have also analyzed the ablation of semiconductor silicon materials, and found the corrugated periodic structures which are different from metal materials. By establishing the relationship between laser power and ablative aperture, the threshold value of monopulse ablation of titanium is 0.20J / cm ~ 2. At the same time, the element composition analysis of different ablation regions after femtosecond laser ablation of silicon target shows that with the increase of pulse number, the oxygen content of ablation region also increases, for the same number of pulses, The oxygen content in different ablation regions is different, and the oxygen content in the ablation center region is obviously higher than that in the edge region, which has a good guiding effect on the fine processing of femtosecond laser in the future. Finally, at the same time, we fixed the incident laser energy, and briefly analyzed the regularity and reason of the ablation morphology and periodic structure of femtosecond laser ablation of copper and titanium under different number of incident laser pulses. The relationship between ablative aperture and pulse number is obtained. When the number of incident laser pulses is small, the ablative aperture increases linearly with the number of pulses, and when the number of incident laser pulses increases to 400, The ablation aperture has little effect on the number of laser pulses. When the energy density of the incident laser is constant, with the increase of the number of pulses, the area of the ablation region increases gradually, and we find a distinct periodic structure at the edge of the ablation region. The effect of pulse number on periodic ripple structure is discussed based on the characteristics of Gao Si distribution and the effect of pulse energy accumulation on laser pulse energy space-time.
【学位授予单位】：山东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN249

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