Increasing productivity of ultrashort pulsed laser ablation for commercialization of micro structuring

Surface functionality is an increasing and crucial factor for the success and acceptance of a product. Through structured surfaces products can gain additional functions. Microstructures enable, for example, friction reduction in combustion engines or optimize the efficiency of LED-based illumination systems. Furthermore, in the area of consumer products optical and haptic functions determine essentially the product quality. The most common way to create surface functionality in mass production are replication processes via structured mold tools. In industrial environment nanosecond pulsed laser sources are established due to their high throughput. Ultrafast laser processing still have shown their advantages characterized by highly precise ablation with minimal thermal influence. Nevertheless, the achieved productivity is still too low for industrial applications in many cases due to the low ablation rate of ultrashort pulse laser processing. To overcome the above mentioned drawback, we investigate ultrashort pulsed laser processing using pulse bursts including pauses to avoid heat accumulation and several scaling strategies like increasing the repetition frequency and enlarging the spot size. The experiments are processed with a pulse duration of 900 fs or 2 ps for productivity reasons. Using average powers of more than 70 W an ablation rate of up to 13 mm3/min is achieved. Not only productivity benefits from burst processing with pauses, but also the surface quality gets significantly improved. The roughness of an ablated surface processed with conventional bursts for example amounts Rα = 5.19 μm while the same burst configuration including a pause produces a surface roughness of Rα = 0.51 μm.