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A: Fachverband Atomphysik

A 9: Interaction with strong or short laser pulses

A 9.1: Poster

Dienstag, 21. September 2021, 16:30–18:30, P

Modeling ultrashort laser pulses in nonlinear media using FDTD — •Jonas Apportin, Christian Peltz, Björn Kruse, Benjamin Liewehr, 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 close to the damage threshold. However, the tight focusing conditions associated with high laser intensities result in non-Gaussian beam profiles that no longer obey the typically applied paraxial approximation, thereby considerably complicating their description within the FDTD framework. We apply an efficient description of such tightly focused beams, based on the decomposition of the laser profile into plane waves and their separate propagation including the compensation of numerical dispersion. The nonlinear 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]. First simulation results for strong and ultrashort laser pulses tightly focused into thin fused silica films (d ≈ 10µ m) show the formation of a pronounced ionization grating due to standing waves at the rear material surfaces.

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

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