Glass welding with ultra-short laser pulses and long focal lengths A process model

Abstract

The welding of glasses with ultra-short laser pulses and high-NA optics has matured to a well-established process. The short focal length requires relatively thin work pieces in the order of 1-2 mm, and the short Rayleigh length requires a very precise adjustment of the laser focus relative to the interface to be welded.To make welding of thick samples possible with relaxed alignment requirements, we welded optically contacted fused silica with a focal length of 65 mm. The resulting welding seams can be as deep as 2 mm and more. It turned out, that they grow from the focal point towards the laser source with increasing pulse energy and irradiation time. A thermal model for the growth of the molten zones will be presented and compared to the process with short focal lengths. Furthermore, the results of tensile tests and helium-leakage tests of welded fused silica samples will be presented.