Ablation Shape Determination under Ultrafast Laser Pulse Irradiation
Based on the time when collisions govern the evolution of the phenomena, modeling of ultrafast laser-dielectrics interactions can be divided into three stages: 1) femtosecond pulse absorption through photon-electron interactions, including electron heating, excitation and generation; 2) electron-ion interactions, including energy transport, phase change and plasma generation; and 3) plasma expansion, shock wave propagation and radiation during plasma-environment interactions. This paper reports our ongoing efforts to investigate ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through the Coulomb explosion and electrostatic ablation. A novel plasma model with quantum treatments is developed to account for significantly varying optical properties. The model is used to successfully predict two uncommon phenomena that were experimentally observed: 1) a flat-bottom crater shape created by a Gaussian beam and 2) repeatable nanoscale structures achieved by pulse train technology. By combining the plasma model and improved two-temperature model, the widely-used assumptions for threshold fluence, ablation depth, and shape in the plasma model based on free electron density are validated by the comparison study and experimental data.
L. Jiang and H. Tsai, "Ablation Shape Determination under Ultrafast Laser Pulse Irradiation," ICALEO, Laser Institute of America, Jan 2008.
International Congress on Applications of lasers & Electro-Optics
Mechanical and Aerospace Engineering
Article - Conference proceedings
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