Welding Fused Silica Glass by Picosecond Pulsed Laser With Low Numerical Aperture

Researches on glass welding using tightly focused ultrafast lasers have attracted much attention. However, optical systems with low numerical aperture (NA) in laser material processing are commonly used in industry applications. Transmission welding of two fused silica glass plates is performed by using picosecond laser irradiation with low NA in this study. The welding strength under different process parameters such as focal position, pulse energy, and scanning velocity is measured. The role of the modification in welding process is demonstrated through the interior morphology in single-piece glass samples. A model is presented to predict the position of the bottom tip of the modification (BTM). The model considers the propagation property of the laser beam and the incubation effect of modification threshold. The numerical and experimental positions of BTM are compared. The model can give an idea for selecting process parameters to the achievement of glass welding for low NA optical system in ultrafast laser welding.