High repetition rate femtosecond laser processing of metals

Previously, in high repetition rate femto second laser processing novel laser matter interacting effects were reported, such as heat accumulation and particle shielding. In this study, high repetition rate laser processing was investigated to discuss and understand the impact of laser repetition rate and accompanied accumulative laser material interacting effects. Therefore, a high repetition rate femto second fibre laser setup joint together with galvo scanner technology was applied in laser micro machining of metals (copper, stainless steel, aluminium). High repetition rate laser processing of aluminium and stainless steel lead to considerably lowered ablation thresholds accompanied with higher ablation rates. Laser ablation behaviour of copper was almost independent of the repetition rate with neither considerable lower ablation thresholds nor higher ablation rates. For explanation, heat accumulation caused by higher repetition rates were assumed as mainly ablation behaviour influencing effect, but thermal material properties have to be considered. Furthermore laser machining examples demonstrate the possibilities and limits of high repetition rate laser processing in 3d micro structuring. Thus, by using innovative scanning systems and machining strategies very short processing times were achieved, which lead to high machining throughputs and attract interest of the innovative laser technology in Rapid Micro Tooling. For discussion, high repetition rate processing results are evaluated by means of comparative machining examples obtained with 1 kHz femto second laser system.