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Optical Engineering

Modeling of ablation threshold dependence on pulse duration for dielectrics with ultrashort pulsed laser
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Paper Abstract

We present a numerical model of plasma formation in ultrafast laser ablation on the dielectrics surface. Ablation threshold dependence on pulse duration is predicted with the model and the numerical results for water agrees well with the experimental data for pulse duration from 140 fs to 10 ps. Influences of parameters and approximations of photo- and avalanche-ionization on the ablation threshold prediction are analyzed in detail for various pulse lengths. The calculated ablation threshold is strongly dependent on electron collision time for all the pulse durations. The complete photoionization model is preferred for pulses shorter than 1 ps rather than the multiphoton ionization approximations. The transition time of inverse bremsstrahlung absorption needs to be considered when pulses are shorter than 5 ps and it can also ensure the avalanche ionization (AI) coefficient consistent with that in multiple rate equations (MREs) for pulses shorter than 300 fs. The threshold electron density for AI is only crucial for longer pulses. It is reasonable to ignore the recombination loss for pulses shorter than 100 fs. In addition to thermal transport and hydrodynamics, neglecting the threshold density for AI and recombination could also contribute to the disagreements between the numerical and the experimental results for longer pulses.

Paper Details

Date Published: 30 November 2016
PDF: 13 pages
Opt. Eng. 56(1) 011026 doi: 10.1117/1.OE.56.1.011026
Published in: Optical Engineering Volume 56, Issue 1
Show Author Affiliations
Mingying Sun, Shanghai Institute of Optics and Fine Mechanics (China)
Electronic Engineering Institute (China)
Jianqiang Zhu, Shanghai Institute of Optics and Fine Mechanics (China)
Zunqi Lin, Shanghai Institute of Optics and Fine Mechanics (China)


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