Stuttgart 2012 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 54: Poster 3

Q 54.40: Poster

Donnerstag, 15. März 2012, 16:30–19:00, Poster.I+II

Controlling ionization mechanisms in high band gap dielectrics via tailored femtosecond laser pulses. — •Thomas Winkler, Cristian Sarpe, Jens Köhler, Matthias Wollenhaupt, and Thomas Baumert — University of Kassel, Institute of Physics and CINSaT, D-34132 Kassel, Germany

Tailored ultrashort laser pulses provide a great potential to control laser induced ionization being the primary step in the ablation process of dielectric materials. In our previous work we have shown that shaped pulses enhance the precision in material processing of transparent dielectrics. For instance pulses generated by cubic spectral phase modulation allow to create structures with sizes one order of magnitude below the diffraction limit by controlling the interplay between multiphoton and avalanche ionization [1]. Here we extrend our previous work [2] with simulations to study the dynamics of the free electron plasma in a thin water jet induced by both bandwidth limited and shaped laser pulses. These simulations, based on numerically solving the rate equation [3] in a refined form [4] for the time dependent free electron density, allow to investigate the dynamics for different temporal pulse shapes. Comparing the simulation results with the experimental data on phase shifts from laser-induced electron density obtained by a precise spectral interference technique we find very good agreement between these two approaches.

[1] L. Englert et al., Appl. Phys. A, 92, 749 (2008), [2] C. Sarpe et al., APL , 88, 261109 (2006), [3] P. K. Kennedy et al., IEEE JQE., 31, 2241 (1995), [4] J. Noack, A. Vogel, IEEE JQE, 35, 1156 (1999)