Stuttgart 2012 – scientific programme

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K: Fachverband Kurzzeitphysik

K 8: Poster II

K 8.4: Poster

Thursday, March 15, 2012, 16:30–18:30, Poster.V

Temporal femtosecond pulse tailoring to control the ionization mechanisms in high band gap materials — Cristian Sarpe, •Nadine Götte, Jens Köhler, Thomas Winkler, Matthias Wollenhaupt, and Thomas Baumert — Universität Kassel, Institut für Physik und CINSaT, Heinrich-Plett-Str. 40, D-34132 Kassel, Germany

The generation of high density free electron plasma is the first step in the laser ablation of dielectric materials. We have shown that tailored ultrashort laser pulses are suitable for robust manipulation of optical breakdown, increasing the precision of ablation one magnitude order below the optical diffraction limit [1, 2]. Here we present our studies to investigate the dynamics of the free electron plasma created by bandwidth limited and shaped femtosecond laser pulses in a thin water jet. By using an extremely stable common path spectral interferometer the phase shift and the contrast of the interference fringes produced between a reference and a probe pulse give accurate information about the density of the plasma and its absorption coefficient. The experimental data are in good agreement with simulation, which are based on a numerical solution of a rate equation of the free electron density [3]. Our measurements directly prove that asymmetric temporal shaped pulses can control the ionization mechanism through which the free electrons are generated in high band gap transparent dielectrics.

[1] L. Englert et al. Opt. Express 15, 17855 (2007)

[2] L. Englert et al. Appl Phys A 92, 749 (2008)

[3] J. Noack and A. Vogel IEEE J. of Quant. El. 35, 1156 (1999)