Investigations on laser micro ablation of steel have been made using multi pulses instead of single pulses. Pulse bursts modify the process regimes, so that the ablation depth and the surface roughness of the ablated area can be improved. For the experiments a ps-laser system at λ= 1064 nm with a pulse duration τ= 12 ps and a repetition rate v= 100 kHz was used. The experiments were carried out with single, double and triple pulses and varying pulse energy in the burst. The interpulse separation Δt{sub}i was varied between 20 and 5000 ns. For the comparison of multi pulse and single pulse ablation the geometry and the roughness of the irradiated area have been measured by white light interference microscopy. Due to the distribution of the energy on several pulses in a burst, the ablation depth was increased up to 90 % compared to single pulse ablation with the same burst energy. A minimal roughness of the ablated surface of R{sub}a = 0.5 μm per triple pulse ablation was achieved.
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