Glass Welding with Ultrashort Laser Pulses Producing mm-long Filaments

The welding of glass with ultrashort pulsed lasers (USP) is usually conducted with optics of high numerical aperture (NA), e.g. microscope objectives. These optics have a working distance of millimeters, limiting the thickness of the workpiece. In addition, they prevent the use of galvanometer scanners, limiting the feed rate of the process. As a step to increase the possible dimensions of the welding partners and the process speed to industrial levels, we present USP-welding with a galvoscanner and an F-theta-lens of 65 mm focal length. Differences between the well-known breakdown-regime and the filamentation-regime shown here regarding the growth of the molten zone and the scaling laws are observed and discussed. The substantial thickness of the samples enables classical mechanical tensile tests with high precision, the results of which are presented.