Milling applications with GHz burst: Investigations concerning the removal rate and machining quality

GHz-bursts were reported to be highly efficient for ultra-short pulse laser ablation compared to single pulses. However, most comparisons were made for a drilling process or the machining of dimples. We investigated GHz-bursts (5.4 GHz) on copper, brass, stainless steel, silicon, zirconium oxide, soda-lime glass and sapphire for surface structuring applications. Inconsistent with the published results neither a higher removal rate, nor an improvement in the machining quality in case of the metals and silicon was observed, in the contrary, a tremendous drop in the specific removal rate of 90% for the metals and 60% for silicon, compared to single pulses, was measured when a 25 pulse burst (maximum of laser system) was applied. The situation differs for zirconium oxide, where only a moderate influence was observed and for soda-lime glass and sapphire where the specific removal rate increased by a factor of 2.3 and 6, when the number of pulses per burst were raised from 1 to 25.