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Proceedings Paper

Femtosecond dynamics of highly excited dielectric thin films
Author(s): Joachim Zeller; Ali J. Sabbah; Mark Mero; Paul M Alsing; John McIver; Wolfgang G. Rudolph
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Paper Abstract

The dielectric constant of several oxide dielectric thin-films (TiO2, Ta2O5 and HfO2) excited close to the laser-induced damage threshold is retrieved from reflection and transmission measurements with a 40-fs time resolution. The experiments were compared with the results of a numerical solution of the coupled Boltzmann equations for conduction band electrons and phonons, including nonlinear carrier excitation and relaxation processes as well as defect formation. The observed fast sub-100-femtosecond decay is shown to be caused by the interaction of non-equilibrium electrons with phonons and is in qualitative agreement with the results of the computer simulation. The observed sign reversal of the real part of the dielectric function from negative to positive after several hundred femtoseconds is attributed to the formation of self-trapped excitons (STE's) in the forbidden bandgap. Both real and imaginary part of the dielectric function are successfully modeled with the Boltzmann equation when defect formation is included. The simulations show that STE formation leads to efficient, non-thermal excitation of phonon modes on a sub-picosecond time scale.

Paper Details

Date Published: 10 June 2004
PDF: 12 pages
Proc. SPIE 5273, Laser-Induced Damage in Optical Materials: 2003, (10 June 2004); doi: 10.1117/12.524456
Show Author Affiliations
Joachim Zeller, Univ. of New Mexico (United States)
Ali J. Sabbah, Univ. of New Mexico (United States)
Mark Mero, Univ. of New Mexico (United States)
Paul M Alsing, Univ. of New Mexico (United States)
John McIver, Univ. of New Mexico (United States)
Wolfgang G. Rudolph, Univ. of New Mexico (United States)

Published in SPIE Proceedings Vol. 5273:
Laser-Induced Damage in Optical Materials: 2003
Gregory J. Exarhos; Arthur H. Guenther; Norbert Kaiser; Keith L. Lewis; M. J. Soileau; Christopher J. Stolz, Editor(s)

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