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Advances in transparent materials processing by ultrashort laser pulses

: Kumkar, M.; Jenne, M.; Grossmann, D.G.; Hecker, S.; Zimmermann, F.; Kleiner, J.; Flamm, D.; Kaiser, M.; Schäfer, M.; Beer, S.; Nolte, S.


Klotzbach, Udo (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Laser-based Micro- and Nanoprocessing XIV : 3-6 February 2020, San Francisco, California
Bellingham, WA: SPIE, 2020 (Proceedings of SPIE 11268)
ISBN: 978-1-5106-3299-8
ISBN: 978-1-5106-3300-1
Paper 112680F, 12 S.
Conference "Laser-Based Micro- and Nanoprocessing" <14, 2020, San Francisco/Calif.>
Fraunhofer IOF ()

During the last years processing of transparent materials by ultrashort laser pulses has gained interest. Spatial and temporal pulse shaping has already proven its potential for advances, widening existing and opening new application fields. The paper focuses on supporting the application development by extending pump-probe diagnostics via combining pulse shaping capabilities, dynamical beam positioning, processing at elevated repetition rates, energy modulation and high temporal resolution over an essentially infinite range of delay. Applying these capabilities gives inside into effects resulting from spatial and temporal shaping, on the laser matter interaction of individual and of a multitude of pulses, the latter typically effective on larger scales due to accumulation. The influence of beam shaping and processing parameters on the dynamic development of the interaction zone in multi pulse exposure highlights the potential of such diagnostic tools. Observations relevant for development of transparent materials processing ultrafast lasers by absorption induced inside of the workpiece are presented. Initiation and development of cracks as a major aspect in brittle materials processing can be analyzed in detail. Pump-probe polarization microscopy for transient stress birefringence observation reveals that both, pressure waves and temperature gradients from accumulation, are of major importance in scaling industrial processing. Considering these findings facilitates addressing different application fields, illustrated by examples on ultrafast welding and selective etching by shaped beams.