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High-throughput micromachining with ultrashort pulsed lasers and multiple spots

: Brüning, Stephan Erich; Du, Keming; Jarczynski, Manfred; Gillner, Arnold


Journal of laser applications : JLA 32 (2020), No.1, Art. 012003, 9 pp.
ISSN: 1042-346X
ISSN: 1938-1387
Journal Article
Fraunhofer ILT ()
ultrashort pulsed laser; diffractive optical element (DOE); 3D microstructure; acousto-optical modulator (AOM)

A one step functionalization of large surfaces and layers could be enabled by high power ultrashort pulsed lasers. Despite today’s availability of high power ultrashort pulsed lasers (up to several hundred watts), it is still a challenge to structure large surface areas, which is required on embossing rollers, within an acceptable processing time for industrial roll-to-roll production. Furthermore, fluencies near the ablation threshold are necessary to provide the highest depth resolution with minor side effects. So, it is a challenge to convert the increasing high average laser power into a high processing speed by maintaining the well-known quality of ultrashort pulsed lasers constant. One approach is the combination of a high-speed application and several parallel ablating laser spots. In this contribution, a newly developed high compact picosecond laser with high pulse repetition rates and an average power of 500W was distributed into 8 and 16 parallel beamlets by a diffractive optical element. The power was controlled by single acousto-optical modulators per beamlet. Different functional surface geometries have been realized on an embossing roller as a master, which is used for the replication of the structures in a roll-to-roll or a roll-to-plate process. Feature sizes from 2 μm to 10μm in areas of 2m2 could be processed. With this approach, functional structures such as reduction in friction, improved soft touch, or light guiding elements can be generated on large surfaces within short processing times.