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Proceedings Paper

Nonequilibrium electron and phonon dynamics in solids absorbing a subpicosecond laser pulse
Author(s): Baerbel Rethfeld; Andreas Kaiser; Martin Vicanek; Gerhard Simon
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Paper Abstract

We study the temporal evolution of the distribution functions of free electron gas in metals and insulators for the case of irradiation with a laser pulse of moderate intensity. A microscopical description on the basis of time- dependent Boltzmann equations is used. The results show the sequence of excitation and relaxation of the electron gas leading eventually to thermal equilibrium. Due to photon absorption the occupation number of electron gas differs significantly from Fermi distribution. For high enough intensities about damage threshold, the energy exchange between electrons and phonos can be described with the two- temperature model. For low excitations we find a delayed energy transfer from laser-excited electron gas to lattice as compared to the two-temperature model. We obtain fluence- dependent thermalization times of the electron gas. For dielectrics we find that the essential process of free- electron generation is strong-electric-field ionization; no avalanche develops in femtosecond time reign. We propose an extended system of two rate equation taking the effect of energy dependence of impact ionization into account. This averaging approach can reproduce the evolution of free electron density in SiO2 with reasonable accuracy.

Paper Details

Date Published: 26 June 2001
PDF: 12 pages
Proc. SPIE 4423, Nonresonant Laser-Matter Interaction (NLMI-10), (26 June 2001); doi: 10.1117/12.431230
Show Author Affiliations
Baerbel Rethfeld, Univ. Essen (Germany)
Andreas Kaiser, Max-Planck-Institut fuer Physik komplexer Systeme (Germany)
Martin Vicanek, Technische Univ. Braunschweig (Germany)
Gerhard Simon, Technische Univ. Braunschweig (Germany)

Published in SPIE Proceedings Vol. 4423:
Nonresonant Laser-Matter Interaction (NLMI-10)
Mikhail N. Libenson, Editor(s)

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