Ablation of solids by femtosecond lasers: Ablation mechanism and ablation thresholds for metals and dielectrics

TLDR

The physics of this new ablation regime involves ion acceleration in the electrostatic field caused by charge separation created by energetic electrons escaping from the target. The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. The authors present an explicit analytical description of the ablation mechanism, deriving formulas for thresholds and rates for metals and dielectrics that account for ion acceleration in the electrostatic field produced by charge separation from escaping electrons, and compare these predictions with experimental data. The study shows that at high intensities the ablation mechanism is identical for metals and dielectrics, and that the calculated dependence of ablation thresholds on pulse duration matches experimental data in the femtosecond regime and relates to nanosecond pulse behavior.

Abstract

The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. It is shown that at high intensities when the ionization of the target material is complete before the end of the pulse, the ablation mechanism is the same for both metals and dielectrics. The physics of this new ablation regime involves ion acceleration in the electrostatic field caused by charge separation created by energetic electrons escaping from the target. The formulas for ablation thresholds and ablation rates for metals and dielectrics, combining the laser and target parameters, are derived and compared to experimental data. The calculated dependence of the ablation thresholds on the pulse duration is in agreement with the experimental data in a femtosecond range, and it is linked to the dependence for nanosecond pulses.