Femtosecond dynamics of highly excited dielectric thin films

Joachim Zeller; Ali J. Sabbah; Mark Mero; Paul M Alsing; John McIver; Wolfgang G. Rudolph

doi:10.1117/12.524456

10 June 2004 Femtosecond dynamics of highly excited dielectric thin films

Joachim Zeller, Ali J. Sabbah, Mark Mero, Paul M Alsing, John McIver, Wolfgang G. Rudolph

Author Affiliations +

Proceedings Volume 5273, Laser-Induced Damage in Optical Materials: 2003; (2004) https://doi.org/10.1117/12.524456
Event: XXXV Annual Symposium on Optical Materials for High Power Lasers: Boulder Damage Symposium, 2003, Boulder, Colorado, United States

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.

Citation Download Citation

Joachim Zeller, Ali J. Sabbah, Mark Mero, Paul M Alsing, John McIver, and Wolfgang G. Rudolph "Femtosecond dynamics of highly excited dielectric thin films", Proc. SPIE 5273, Laser-Induced Damage in Optical Materials: 2003, (10 June 2004); https://doi.org/10.1117/12.524456

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