Collaborative Research: Modeling and Analysis of High Energy Ultrashort Laser-Induced Plasmas and Shockwave

这个项目的目标是通过建模和实验来了解和控制高能、超短激光-固体相互作用过程中等离子体和冲击波的形成。特别是，将研究在固体表面附近出现的早期等离子体，该表面受到高能、超短激光的照射。一个目标是控制冲击波和等离子体的性质，以便它们可以被利用来产生新的结果，如灯丝效应，即由于自聚焦和等离子体去聚焦之间的动态平衡而形成的等离子体颤振。这项研究将有助于开发一种与使用超短、高功率激光相关的激光-物质相互作用的合适建模技术。多尺度混合模型将被用来研究早期等离子体的形成及其与激光和靶面的相互作用。对于早期等离子体的形成，将发展一个分子动力学和蒙特卡罗联合模型(MD/MC)来计算中性粒子、电子、离子、光子和声子的动力学，同时考虑这些粒子之间的相互作用。由于计算的复杂性，MD/MC组合的时间和空间计算域的大小是有限的，因此MD/MC将与靶材内部区域的有限差分模型对接，并与靶面上方区域的流体动力学方程对接，以模拟等离子体/环境空气区域。这个组合模型将揭示早期等离子体形成的详细信息，以及它与激光和靶面的相互作用。在配套的实验研究中，将利用干涉图和阴影技术实现对不同延迟时间激光产生的等离子体和冲击波的更全面的测量和观测。实验结果将用于模型的验证。高能、超短激光的应用范围从脉冲激光制造薄膜到激光微/纳米制造。提高对高能超短激光-材料相互作用的认识，可以极大地扩展这些器件的潜在应用。这项研究将产生与未来开发适用于特定应用的激光器相关的信息。研究结果将在针对工业界和学术界受众的会议上广泛传播，并将在一个专门的网站上传播。几名本科生将通过普渡大学工程学院管理的夏季本科生研究奖学金(SURF)计划以及本科生独立项目参与其中。将通过妇女参与工程方案(WEP)和少数民族工程方案(MEP)等现有方案，促进代表人数不足的学生的参与。这项研究将被纳入本科生的制造课程，制造过程的原理和实践。在伊利诺伊理工学院(IIT)，新的发现将被纳入一门名为先进制造工程的课程。本科生和少数族裔研究生将通过本科生研究奖学金计划和IIT的专题课程参与其中。基于该项目的动画演示套件将与芝加哥公立学校学生科学博览会分享，以吸引更多学生(特别是少数族裔学生)投身科学和工程领域。

0853528WuThe goal of this project is to develop an understanding of, and ability to control plasma and shock wave formation during high energy, ultrashort laser-solid interaction via modeling and experimentation. In particular, the early plasma that occurs near a solid surface that is irradiated by high energy, ultrashort laser beams will be investigated. A goal is to control the shock wave and plasma properties so that they may be exploited to create novel results such as filament effects, i.e., formation of a plasma chatter that results from the dynamic balance between self-focusing and plasma de-focusing. The research will enable development of a suitable modeling technique for laser-matter interaction that is associated with the use of ultrashort, high power lasers.Intellectual Merit. A multi-scale hybrid model will be developed to investigate the early plasma formation, its interaction with the laser beam and the target surface. For the formation of early plasma, a combined molecular dynamics and Monte Carlo model (MD/MC) will be developed to calculate the dynamics of neutrals, electrons, ions, photons and phonons, while considering the interactions among these particles. Since the temporal and spatial computation domain sizes of the combined MD/MC are limited because of computational complexity, the MD/MC will be interfaced with a finite difference model for the domain deep inside the target material, and also interfaced with the hydrodynamic equations for the domain above the target surface to model the plasma/ambient air region. This combined model will reveal detailed information about early plasma formation, and its interaction with the laser beam and the target surface. In the companion experimental study, the interferogram and shadowgraph techniques will be used to realize a more comprehensive measurement and observation of laser-generated plasma and shock waves at different delay times. The experimental results will be used for the validation of the model.Broader Impacts. High energy, ultrashort lasers have applications ranging from pulsed laser fabrication of thin films to laser micro/nano fabrication. Improving the understanding of high energy ultrashort, laser-material interaction can significantly expand the potential applications of these devices. The research will yield information relevant to the future development of suitable lasers for specific applications. The research results will be broadly disseminated at conferences targeted to both industrial and academic audiences, as well as at a dedicated web site. Several undergraduate students will be involved through the summer undergraduate research fellowship (SURF) program administered by the College of Engineering at Purdue, as well as through undergraduate independent projects. Involvement of underrepresented students will be pursued through existing programs such as Women in Engineering Program (WIEP) and the Minority Engineering Program (MEP). The research will be incorporated into an undergraduate manufacturing class, Principles and Practice of Manufacturing Processes. At the Illinois Institute of Technology (IIT), the new findings will be incorporated into a class entitled Advanced Manufacturing Engineering. Undergraduates and minority graduate students will be involved through the Undergraduate Research Fellowships program and a Special Topics class at IIT. Animation demonstration kits based on the project will be shared with the Chicago Public School Students Science Fair, to attract more students (particularly minority students) to become engaged in science and engineering.