Ultrashort Pulse Processing of Transparent Ceramics: The Role of Electronic and Thermal Damage Mechanisms

In this study, we investigate the ultrashort pulse processing of the transparent, so-called, spinel ceramic (MgAl2O4). We examine the dominant underlying damage mechanisms by an adjustment of the processing parameters. The applied pulse duration is varied from 2 ps to 80 fs to investigate the impact of the electronic and thermal damage mechanisms on the observed modifications in the material. For surface structuring or ablation cutting conditions, pulse repetition rates below 1 MHz are used leading to electronic damages in form of micro-cracks and spikes inside the volume for pulse durations from 1 ps to 2 ps. By a decrease of the pulse duration to 80 fs, we are able to reduce the electronic damages due to a higher absorption of the laser pulse energy at the spinel surface. By an increase of the pulse repetition rate to 2 MHz, we find evidence for thermal melting of the spinel surface due to the impact of heat accumulation, which leads to a loss of the unique structural properties of the spinel.