Influence of laser beam’s image-plane position on geometry of through-holes in percussion-drilled glass using excimer laser

We study the influence of a laser beam’s image-plane position relative to the processed surface for the deep-hole, laser-microdrilling of soda-lime glass with an excimer 308-nm laser and mask-projection technique. It is demonstrated that the image-plane position has a significant influence on the hole’s tapering and final depth. Holes with exit diameters up to 10 times smaller than the mask-image diameter are produced in the case of perforation during the appropriate process phase determined by the formation of the plasma plume.