Reduction of stress cracking in micromachining of glass by preheating of samples

Abstract

Laser micromachining may be used for a variety of applications including drilling holes or creating trenches in dielectric materials. Cracking around the ablated features can be a significant problem for many applications, particularly when micromachining glass. One possible method for crack reduction, investigated here, involves heating of the substrate during ablation. This leads to a more ductile material that is more able to withstand the thermal shock of the ablation process. In order to increase the ductility, the glass targets are heated by physical contact with an electric heating element. The results of micromachining are analyzed using an optical microscope. The amount of cracking is quantified in terms of the number of visible radial cracks. For nanosecond micromachining, a reduction in the number of cracks and an improvement in the quality of the holes are observed as the glass is heated. The relative improvement using heated substrates and nanosecond pulses is also compared to femtosecond ablation of room temperature substrates.

High temperature thermal behaviour modeling of large-scale fused silica optics for laser facility

“…Several methods of controlling the stress of op-tics have been studied, such as preheating before laser irradiation [9] controlling cooling rate after laser irradiation, [10] and high temperature annealing after laser irradiation and cooling to ambient temperature. High temperature annealing is one of the methods which is more widely researched and more efficient in applications.…”