Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 39: Phase transitions

O 39.2: Talk

Tuesday, March 23, 2010, 15:15–15:30, H42

Modelling laser-induced dielectric breakdown: Application of the multiple rate equation — •Oliver Brenk, Nikita Medvedev, and Baerbel Rethfeld — TU Kaiserslautern, 67663 Kaiserslautern, Deutschland

Material processing with ultrashort laser pulses is in the focus of experimental and theoretical research. In order to provide a tool for numerical simulation of the effects of ultrashort laserpulse irradiation on dielectrics the multiple rate equation (MRE) has been introduced [1]. The MRE allows to investigate the temporal evolution of the electronic density in the conduction band with very good agreement to a full kinetic approach [2], using Boltzman's equation, but with considerably less computational effort. We have extended the MRE model to include additional effects, namely the reflectivity and the recombination into Self-Trapped Excitons (STE-States). The reflectivity, depending on the electronic density, influences the laser intensity inside the material. STEs are localized electron-hole pairs formed by free electrons having recombined with localized holes, energetically lying between valence band and conduction band. Re-excitation out of these states is considered as well. We study the influence of these processes on the optical parameters and on the threshold behavior of dielectric breakdown. To further expand the model we plan to add a spatial dimension, to study the spatially resolved evolution of the electronic densities to the already implemented time evolution.

[1] B. Rethfeld, Phys. Rev. Lett., 92:187401, 2004.

[2] A. Kaiser et al., Phys. Rev. B, 61:11437, 2000.