Electron dynamics in transparent materials under high-intensity laser irradiation

Oliver Brenk; Bärbel Rethfeld

doi:10.1117/1.OE.51.12.121810

22 August 2012 Electron dynamics in transparent materials under high-intensity laser irradiation

Oliver Brenk, Bärbel Rethfeld

Author Affiliations +

Optical Engineering, Vol. 51, Issue 12, 121810 (August 2012). https://doi.org/10.1117/1.OE.51.12.121810

Abstract

The energy of a laser beam irradiating a surface is primarily absorbed by electrons within the solid. In actual transparent materials, absorption is low. High-intensity lasers may, however, be absorbed by initially bounded electrons through nonlinear processes. The increase of free-electron density leads eventually to dielectric breakdown, and the material becomes highly absorbing. We present theoretical studies on the dynamics of electrons in dielectrics under irradiation with a visible high-intensity laser pulse. We consider microscopic processes determining absorption, redistribution of the energy among electrons, and transfer of energy to the crystal lattice. We review different aspects of electronic excitation, studied with time-resolved models as the Boltzmann kinetic approach and the time and spatial resolved multiple rate equation. Furthermore, we investigate criteria for damage thresholds. Two concepts are compared, namely a critical free-electron density and the melting threshold of the lattice. We show that in dielectrics both criteria are fulfilled simultaneously. Optical parameters depend on the density of free electrons in the conduction band of the solid, so the free-electron density directly leads to an increased energy absorption causing material modification. We present results on the spatial dependence of dielectric breakdown.

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Oliver Brenk and Bärbel Rethfeld "Electron dynamics in transparent materials under high-intensity laser irradiation," Optical Engineering 51(12), 121810 (22 August 2012). https://doi.org/10.1117/1.OE.51.12.121810

Published: 22 August 2012

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