纳米结构辅助基底表面近场增强的数值模拟研究

发布时间：2018-05-04 18:46

本文选题：飞秒激光 + 近场光学　；参考：《长春理工大学》2017年硕士论文

【摘要】：利用纳米结构对飞秒激光能量进行局域而获得近场的增强,进行纳米尺度下光与物质相互作用过程的控制,可以实现超衍射空间尺度的纳米加工。本文以飞秒激光近场超衍射纳米孔加工及周期纳米条纹结构制备为应用背景,利用有限时域差分法(FDTD),对基于纳米结构辅助粒子近场增强(粒子与基底接触处的电场增强)及其散射场周期条纹分布进行了数值模拟,并对其增强机理及波纹形成物理过程进行了分析。在利用纳米结构辅助实现超衍射纳米加工的近场增强研究方面,通过对近场纳米加工用典型辅助粒子(Au、Si和TiO_2)经激光辐照后近场分布特性的分析,提出了应用高折射率TiO_2介电粒子阵列作为辅助手段诱导激光近场增强的新方案,利用FDTD数值计算方法对其进行了模拟研究。结果发现,TiO_2粒子将激光能量局域到粒子周围约100nm空间范围内,其空间尺度可以突破衍射极限。而Ti O_2阵列相比于单一粒子,其近场增强幅度下降小于30%,但相对于入射激光而言,仍具有140倍的增强,这非常有利于飞秒激光超衍射加工。同时,理论结果也表明,几乎在所有金属及介电材料表面都可以实现良好的近场增强效果,并且具有随着基底折射率增加近场逐渐增强的影响规律。这些现象的产生归因于TiO_2粒子磁四极振荡吸收的激光前向场增强效应以及粒子与基底近场相互作用过程的结果。我们获得的以上结果对飞秒激光超衍射近场纳米加工的应用有着重要的意义。应对目前飞秒激光直接辐照基底表面形成的周期条纹制备的图案单调以及结构清晰度难以保证的不足,开展了材料表面纳米结构散射场的周期分布研究。利用球形、正六面体、长方体等典型纳米结构计算了其散射场的周期分布,发现纳米结构的形状、材料及空间分布(纳米结构数量在两个以上时)对其基底表面散射场分布及强度均有显著影响,并可以通过改变纳米结构参数进行条纹分布的优化和控制。这一研究结果,为超衍射极限空间尺度纳米周期条纹结构的制备与优化打下了基础。
[Abstract]:The near field enhancement of femtosecond laser energy is obtained by using nanostructures, and the process of interaction between light and matter at nanometer scale can be controlled, which can realize superdiffraction nanomechanism on spatial scale. In this paper, femtosecond laser near-field superdiffraction nano-hole fabrication and periodic nano-stripe structure preparation are used as the application background. Based on the near field enhancement (electric field enhancement at the contact between particle and substrate) and the periodic fringe distribution of scattering field, the FDTD method is used to numerically simulate the near field enhancement of particles based on nanostructure. The mechanism of enhancement and the physical process of ripple formation are also analyzed. In the near field enhancement study of superdiffraction nanoprocessing by using nanostructure, the near field distribution characteristics of typical auxiliary particles such as Au-Si and TiO-2) after laser irradiation are analyzed. A new scheme of laser near field enhancement induced by high refractive index TiO_2 dielectric particle array is proposed and simulated by FDTD numerical method. The results show that the laser energy is localized to the 100nm space around the particle, and the diffraction limit can be broken by the space scale of TiO-2 particles. Compared with a single particle, the near field enhancement of TiO2 array is less than 30%, but it is still 140 times higher than that of incident laser, which is very favorable to femtosecond laser superdiffraction processing. At the same time, the theoretical results also show that almost all metal and dielectric materials surface can achieve good near field enhancement effect, and with the increase of substrate refractive index, the near field increases gradually. These phenomena are attributed to the laser forward-field enhancement effect of the magnetic quadrupole absorption of TiO_2 particles and the near field interaction between the particles and the substrate. The above results are of great significance to the application of femtosecond laser superdiffraction near field nanocrystalline processing. The periodic distribution of scattering field of nanoscale structures on the surface of materials was studied in order to overcome the monotonous pattern of periodic fringes formed by femtosecond laser irradiation on the substrate surface and the difficulty in ensuring the clarity of the structure. The periodic distribution of scattering field was calculated by using spherical, hexahedron, cuboid and other typical nanostructures, and the shape of nanostructures was found. The material and spatial distribution (when the number of nanostructures is more than two) has a significant effect on the distribution and intensity of scattering field on the substrate surface, and the fringe distribution can be optimized and controlled by changing the parameters of the nanostructure. The results lay a foundation for the preparation and optimization of nanoscale periodic fringes in super-diffractive limit space.
【学位授予单位】：长春理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN249;TB383.1

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