Hannover 2003 – scientific programme

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MO: Molekülphysik

MO 3: Nichtlineare Femtosekunden-Effekte (gemeinsame Sitzung mit FV Q)

MO 3.1: Talk

Monday, March 24, 2003, 15:00–15:15, E001

Investigation of the electron plasma generation during the optical breakdown of femtosecond laser ablation — •Cristian Sarpe-Tudoran, Andreas Assion, Matthias Wollenhaupt, Christian Horn, Marc Winter, and Thomas Baumert — Universität Kassel, Fachbereich Physik, Heinrich-Plett-Str. 40, D-34132 Kassel

The application of ultrafast lasers for high-quality material processing is an exciting field that has grown rapidly in the past few years. The use of femtosecond laser pulses is especially interesting for transparent media and nanostructuring. It is generally accepted that in the beginning of the laser induced breakdown a high density free electron plasma is created by multiphoton absorption and avalanche ionization, whereas the first becomes dominant in the femtosecond regime. But still the creation of the electron plasma and the ablation mechanism with femtosecond pulses is not completely understood. In this work we investigate the electron plasma dynamics in the early stage of formation by transient reflection spectroscopy techniques during the optical breakdown. In a collinear pump-probe set-up a high intensity ultrashort laser pulse creates the free electrons and a time delayed weak one is reflected by the plasma. By analyzing the back reflected spectrum the breakdown threshold and the rise and decay characteristic times of the high density plasma are obtained. Additionally, by means of laser induced breakdown spectroscopy we are able to determine the ablation efficiency. First experimental results are presented and will be discussed.