Erlangen 2022 – scientific programme

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A: Fachverband Atomphysik

A 10: Interaction with strong or short laser pulses

A 10.5: Poster

Tuesday, March 15, 2022, 16:30–18:30, P

Modeling ultrafast plasma formation in dielectrics using FDTD — •Jonas Apportin, Christian Peltz, Benjamin Liewehr, Björn Kruse, and Thomas Fennel — Institute for Physics, Rostock, Germany

The Finite-Differences-Time-Domain (FDTD) method provides a real-time solution to Maxwell’s equations on a spatial grid that can be easily extended by rate equations for e.g. ionization and is therefore optimally suited for the modeling of nonlinear laser-material interaction and plasma formation in dielectrics close to the damage threshold. The material response is modeled using nonlinear Lorentz oscillators for Kerr-type nonlinearities [1] and Brunel as well as injection currents associated with the excitation of electrons into the conduction band for higher order nonlinearities [2]. Along with strong field ionization, plasma formation is induced by impact ionization which is strongly dependent on the electron velocities. To avoid simulating the full electron velocity distributions required for the calculation of the impact ionization rates, we apply an effective rate equation model for the electron temperatures and drift velocities, by estimating equilibrium distributions. First simulation results for strong and ultrashort laser pulses tightly focused into thin fused silica films (d ≈ 10 µ m) show the formation of a pronounced ionization grating.

[1] C. Varin et al., Comput. Phys. Commun. 222 70-83 (2018)

[2] P. Jürgens et al., Nature Physics 160, 1035-1039 (2020)