Large Scale Ultrafast Laser Micro Texturing with Multi-Beams

Today ultrashort pulse lasers (USP lasers) are already widely used to realize highly precise micro-structures directly in nearly any material. Despite of today's availability of high power ultrashort pulse lasers (up to several hundred watts), it is still a challenge to structure large surface areas, as required on embossing rollers, within an acceptable processing time for industrial production. A newly developed high compact ps-laser with repetition rates of up to 8MHz and an average power of up to 500W was distributed into 8 parallel beamlets by a diffractive optical element (DOE). Each of the single beams in the array is controlled by an acousto optical modulator (AOM). The beam array was focused on a cylinder surface with spot sizes of 10 mu m. Based on this initial set up, a further improved optical systems with 16 single beams has been designed to increase ablation speed and productivity. The beams have a distance of 20 mu m (8 beamlets) respective 80 mu m (16 beamlets) from spot to spot. Integrated in an ultra-high precision cylinder engraving system, the spots were synchronized with a precision of <l mu m. Different functional surface geometries have been realized on an embossing roller as a master, which is used for the replication of the structures in roll-to-roll (R2R) processes. With this setup, functional structures as e.g. reduction in friction, improved soft touch or light guiding elements can be generated on large surfaces within short processing times.