Investigation on material removal efficiency in debris-free laser ablation of brittle substrates

For decades, it is a big challenge to machine glasses even using non-contact machining technology such as laser machining. The study investigated the influence of laser beam scanning mode on material removal efficiency in laser ablation of Gorilla glass using ps NIR laser pulses. The study revealed that crack-free and debris-free ablation could be achieved by optimizing beam overlaps. Optimal scanning speed was above 200 mm/s with a few pulses overlapped in one ablation spot during scanning. When laser was focused at glass bottom surface, laser energy was more efficiently employed for glass ablation due to negligible energy dispersion caused by ejected materials. The cutting time was 1.36 times and 24.5 times longer for focus at glass center and top surface, respectively. The cut kerf width was found to correlate with scanning line numbers. Optimal kerf for high material removal rate was approximately half of the glass thickness. Optimal shifting pitch between two lines was approximately a single scan line width, namely an ablation spot diameter. The cutting time was 1.51 times and 13.43 times longer for merge-mode and group-mode, respectively, when compared to scanning with raster-mode. Fixed parameter mode reduced 86% of cutting time compared to non-fixed parameter mode. Similar protocol of scanning mode for high material removal efficiency was applicable to ps NIR laser ablation of aluminosilicate glass and ns UV laser ablation of silicon substrate. Mathematical model for calculation of beam overlaps, scanning speed and line number was provided.