Laser micro processing using a high repetition rate femto second laser

The paper presents an overview about high repetition rate femto second laser machining and its applications. Novel phenomena in laser matter interaction with the repetition rate as one of the mainly influencing parameter are discussed. Depending on temporal distances between consecutive femto second laser pulses, either heat accumulation or particle shielding effects were detected. Heat accumulation enhanced the ablation behavior and higher ablation rates were found. On other hand energy losses due to particle shielding caused lowered ablation rates. Furthermore laser induced periodical surface structures, such as ripple formations and conical micro structures, were observed due to the high average laser energy input and accumulative effects. Formation und shape properties of these structures depend on laser processing parameter. Joining high repetition rate laser technology together with high speed beam deflection systems, significantly higher ablation rates and short processing times were achieved. Exemplarily demonstrated in 3D micro structuring, processing times were reduced more than 40 times compared to fs laser processing using repetition rates of some kHz. In consequence, prospectively high machining throughputs were reached, which attract increasing interest of the novel technology in industrial applications.