Jena 2013 – wissenschaftliches Programm
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K: Fachverband Kurzzeitphysik
K 9: Laseranwendungen und Lasermaterialbearbeitung III
K 9.2: Vortrag
Donnerstag, 28. Februar 2013, 16:45–17:00, HS 4
Analysis of the hole formation in ultrashort pulse laser deep drilling — •Sven Döring1, Tobias Ullsperger1, Sören Richter1, Andreas Tünnermann1,2, and Stefan Nolte1,2 — 1Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Germany — 2Fraunhofer Institute for Applied Optics and Precision Engineering, Jena, Germany
We present a detailed experimental study of the hole formation process during ultrashort pulse laser deep drilling in silicon by in-situ imaging. This technology allows to directly follow the evolution of the hole shape inside a material which is opaque for the drilling radiation. Our observations show three characteristic phases of the drilling process for all parameters. At first, the hole capillary is excavated with high reproducibility. In a second phase, the drilling rate undergoes statistical variations which involve the formation of imperfections like bulges and multiple hole ends. Finally, forward drilling stops and only the diameter of the hole can increase further. Our investigation of the influence of process parameters like pulse energy and focus position on this behavior revealed an increase of the achievable hole depth up to a factor of 2 by optimizing the focus position, while minimizing the statistical variations.