Excitation and relaxation dynamics of electrons and phonons in solids absorbing subpicosecond laser pulses

Baerbel Rethfeld; Andreas Kaiser; Martin Vicanek; Gerhard Simon

doi:10.1117/12.376966

1 February 2000 Excitation and relaxation dynamics of electrons and phonons in solids absorbing subpicosecond laser pulses

Baerbel Rethfeld, Andreas Kaiser, Martin Vicanek, Gerhard Simon

Author Affiliations +

Proceedings Volume 3885, High-Power Laser Ablation II; (2000) https://doi.org/10.1117/12.376966
Event: Advanced High-Power Lasers and Applications, 1999, Osaka, Japan

Abstract

The distribution function of free electron gas in metals and insulators for the case of irradiation with a laser pulse of moderate intensity is calculated. A microscopical description on the basis of time-dependent Boltzmann equations is used. For the metal, photon absorption by free electrons, electron-electron collisions and electron-phonon collisions are considered each by a corresponding collision integral. In dielectrics, additional terms for two ionization processes (strong-electric-field ionization and impact ionization) are included. We choose aluminum as a representative of a metal and SiO₂ for modeling an insulator. The results show the sequence of excitation and relaxation of the electron gas. Due to photon absorption the occupation number of electron gas differs significantly from Fermi distribution. For metals we show that electron thermalization to a Fermi distribution occurs rapidly within less than hundred femtosecond after irradiation ended. For dielectrics we find that for pulses shorter than about 100 fs, impact ionization is negligible in comparison with strong-electric-field ionization. We shown that in this case impact ionization can not be described by simple rate equations.

Citation Download Citation

Baerbel Rethfeld, Andreas Kaiser, Martin Vicanek, and Gerhard Simon "Excitation and relaxation dynamics of electrons and phonons in solids absorbing subpicosecond laser pulses", Proc. SPIE 3885, High-Power Laser Ablation II, (1 February 2000); https://doi.org/10.1117/12.376966

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