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W. Husinsky:
"Interaction of ultrashort laser radiation with metals: Laser-SNMS for surface analysis, pulse width dependence and genetic learning algorithms to optimize the ablation process";
Vortrag: Seminar Institut für Allgemeine Physik (IAP), TU Wien; 16.11.2004.

Laser ablation of metals with ultrashort laser pulses represents an interesting field, both with respect to various applications (material processing, surface analysis etc.) and also from the viewpoint of the physics involved.
Recent results of ultrashort laser ablation for laser SIMS and laser SNMS will be presented. The understanding of the physics of the ablation process is a necessity for useful applications. Although we are still far from a detailed understanding for even simple systems as metals, pump-probe experiments, measurements of the energy distribution of ablated species and pulse-width dependence studies have brought substantial insight. Recent results will be discussed.
Pulse shaping allows forming a particular time evolution of the pulse with a characteristic frequency chirp as a function of time. Pulse shaping cannot be performed in the time domain, but is usually achieved in the frequency domain. In practice, two methods have been reported to realize a pulse shaper: A combination of gratings and LCD or an opto-acoustic-dazzler. We have used an acousto-optic dispersive filter in combination with a FEMTO PRO amplifier system. Due to the limitations of the crystal and our laser system, we can vary the pulse lengths from 25 fs up to approximately 3 ps. Intensity and phase of the individual frequency components can be modified arbitrarily. Hence a flexible pulse form can be achieved in this time frame. The principle optimization via self-learning algorithms and pulse-shaping and first results for laser ablation will be reported in the second part of the talk