Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 39: Phase transitions

O 39.4: Vortrag

Dienstag, 23. März 2010, 15:45–16:00, H42

New self-consistent model of ultrashort laser irradiation of materials — •Nikita Medvedev and Baerbel Rethfeld — Technical University of Kaiserslautern, Department of Physics, Erwin Schroedinger Str. 46, 67663 Kaiserslautern, Germany

We present a new model describing femtosecond laser interaction with a semiconductor or dielectric target. Based on the earlier developed Multiple Rate Equations [1], the model includes interaction of electrons with the phononic subsystem, allowing direct determination of conditions for crystal damage. Taking into account dynamical changes of the optical properties of the target (reflectivity, absorption coefficients), the developed model gives access to a criterion of the damage self-consistently, tracing a change of optical properties as well as a lattice heating and melting.

In contrast with commonly used approaches based on the thermodynamical description of the material (like two temperature model), our model is widely applicable for nonequilibrium electronic conditions, where one cannot use such thermodynamical property as temperature. On the other hand, the model is still simple to use. Applying experimental parameters, we found perfect agreement with the measured reflectivity of the material during irradiation with a femto-second laser pulse and also obtained the damage fluence threshold in very good agreement. The developed model is a powerful tool to describe the dynamics of the electronic subsystem as well as lattice heating.

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