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Proceedings Paper

Electron dynamics in transparent materials under high-intensity laser irradiation
Author(s): Oliver Brenk; Baerbel Rethfeld
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Paper 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. Further we investigate criteria for damage thresholds. Two concepts compare, 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.

Paper Details

Date Published: 28 November 2011
PDF: 15 pages
Proc. SPIE 8190, Laser-Induced Damage in Optical Materials: 2011, 81901W (28 November 2011); doi: 10.1117/12.899189
Show Author Affiliations
Oliver Brenk, Technische Univ. Kaiserslautern (Germany)
Baerbel Rethfeld, Technische Univ. Kaiserslautern (Germany)

Published in SPIE Proceedings Vol. 8190:
Laser-Induced Damage in Optical Materials: 2011
Gregory J. Exarhos; Vitaly E. Gruzdev; Joseph A. Menapace; Detlev Ristau; M. J. Soileau, Editor(s)

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