Oblique incidence of ultrafast laser for glass butt welding.

Lap welding restricts the connection state of glasses by vertically incident ultrafast laser at the interface to be welded, which cannot meet the increasingly flexible welding needs. In this Letter, glass butt welding is achieved by oblique incidence of an ultrafast laser, expanding the applicability of ultrafast laser glass welding. Furthermore, the propagation path of the laser beam after oblique incidence into a glass is solved based on geometric optics, the dynamic development of the molten pool in a glass is observed through a high-speed camera, and the mechanism of glass butt welding is elucidated. Finally, the influence of laser pulse energy, glass tilt angle, and defocus amount on welding strength is investigated, achieving a maximum shear strength of 11.5 MPa.

Ultrafast laser bursts welding glass and metal with solder paste to create an ultra-large molten pool.

A novel, to our knowledge, method is proposed for the welding of glass and metal with a large gap filled with solder paste using ultrafast laser bursts. The addition of solder paste enables a reliable glass-metal connection even at gaps of hundreds of microns, while the position of the glass can be flexibly adjusted. By ultrafast laser bursts, the volume of the molten pool increases significantly, and the height of the molten pool reaches approximately 350 µm, which is more than an order of magnitude higher than that of conventional ultrafast lasers (10-20 µm). Cross-sectional analysis of the welded region shows that extensive material mixing and element diffusion occur, and stable connections are achieved at multiple interfaces. An analysis of the interaction between the ultrafast laser bursts and the material, as well as the mixing of multiple materials during the welding process, leads to a clear welding mechanism.

Prediction of internal modification size in glass induced by ultrafast laser scanning.

The modification at the interface between glass plates induced by ultrafast laser is important for the glass welding strength, therefore the relationship between the modification size and processing parameters should be identified. The experimental method has its limitation in understanding the nature of the modification. In this study, a numerical model for the temperature distribution determining the modification size induced by ultrafast laser scanning is developed, in which a three-dimensional steady model for the beam propagation with a transient ionization model is established to estimate the free electron density by the single laser pulse, and then a heat accumulation model for multiple laser pulses is employed to describe energy transportation within the irradiated bulk. The experiment for the internal modifications in single-piece fused silica samples irradiated by a picosecond laser with different pulse energies and scanning velocities is performed to validate the present model.