Dresden 2009 – scientific programme

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SYSO: Symposium Self-organizing Surfaces and Interfaces

SYSO 3: Self-Organizing Surfaces and Interfaces - Posters

SYSO 3.25: Poster

Wednesday, March 25, 2009, 17:30–19:30, P3

Feedback effect on the self-organized structures formation upon femtosecond laser ablation — •Olga Varlamova and Juergen Reif — LS Experimentalphysik II, Brandenburg University of Technology Cottbus and IHP/BTU JointLab Cottbus, Konrad-Wachsmann-Allee 1, 03046 Cottbus, Germany

Self-organized structures upon multi-pulse femtosecond laser ablation at intensities below the ablation threshold for a single pulse for CaF2 and around the ablation threshold for Si are observed at the crater bottom. Numerous experimental data exhibit a positive feedback in the self-organization process. To investigate an influence of this effect on the formation of surface structures ablation experiments with variable pulse separation time have been performed on semiconductor (Si) and dielectric (CaF2). By reducing laser repetition rate from 1000 Hz to 1 Hz we observe an exponential decrease of the ablated area on both samples. The results for Si show also an essential reduction of the pattern complicity as well as of their size in the centre of the ablation spot. We show that feedback becomes weaker with increasing time intervals between successive pulses. The nature of the feedback mechanisms will be discussed.