Long Focal Length Green Femtosecond Laser Welding of Glass

In ultrafast laser glass welding, the laser beam is usually focused by a large numerical aperture micro objective lens. The welding is strictly limited to a very small focal volume with short working distance, low welding speed, and narrow weld width, which limit its industrial applications. In this work, a 75 W green femtosecond laser equipped with a 255 mm-long focal scanning galvanometer was employed to achieve non-optical contact high-speed welding of display screen glasses. The effects of the focal position, pulse energy, and scanning speed on the weld formation were obtained, the welding process window was also obtained. An extremely high welding speed of 6 m/min was achieved without weld defects. In addition, the welds exhibited a shear strength of 20 MPa as well as good seal performance and transmittance, indicating that our method has a great prospect in industrial applications.