The 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.
