Laserabtrag mit zeitlicher Modulation der Energiedeposition

• Laser structuring with temporal modulation of the energy deposition

Hartmann, Claudia; Poprawe, Reinhart (Thesis advisor)

1. Aufl.. - Aachen : Publikationsserver der RWTH Aachen University (2014)
Book, Dissertation / PhD Thesis

In: Ergebnisse aus der Lasertechnik
Page(s)/Article-Nr.: II, 157 S. : Ill., graph. Darst.

Aachen, Techn. Hochsch., Diss., 2013

Abstract

For laser structuring of surfaces different influencing factors control the ablation process and quality of the structured surface. These factors occur during and after the laser pulse hits the surface. They influence absorption, heating and plasma expansion and therefore change the ablation rate and surface roughness. The influence of the different factors depends on the pulse duration and pulse shape. The aim of this thesis is to maximize the ablation rate while minimizing the surface roughness in comparison to the ablation with single pulses. This is achieved by an adaption of the temporal energy deposition. Furthermore the influencing factors of the ablation process are investigated and evaluated. The six major influencing factors are pre-heating of the material by previous pulses, change of the absorption coefficient by pre-heating, heat penetration depth in the material, absorption of laser radiation in plasma, expansion of the blast wave in pulse bursts and interaction of the plasma with the structured surface. For these investigations ablation experiments are examined with respect to the ablation rate and surface quality. Also the plasma and blast wave expansion is studied. The investigation is done both with pulse durations at ns and ps range. Different modulations of changed energy deposition are examined. These variations are changed pulse shape, pre- and post-heating as well as pulse bursts.