Holographic multi-spot generation for ultra-short pulse Bessel beam processing of stainless steel.

Spatial Light Modulators are widely used for creating multiple laser spots with a flexible spatial distribution. This work presents an optical setup for multi-spot laser micro-drilling on stainless steel. For decreasing the hole diameter and getting high laser spot intensities, Bessel beams were generated. A phase only SLM was used as a beam splitter and a physical axicon was added to the setup. This separation of beam splitting and shaping is due to the higher diffraction efficiency of the axicon compared to holographic generated Bessel beams, especially for high cone angles. Minimizing the intensity losses is important due to the low damage threshold of SLM displays. Furthermore, additional lenses has been added for increasing the spot intensity. An ultra-short pulse Ti:Sa-laser (800 nm, 100 fs) was used for the experiments. Possible Bessel spot distributions for metal processing and the impact of the mutual influence of the spots were investigated. [ABSTRACT FROM AUTHOR]