Glass micro welding in thermal accumulation regime with using spatially shaped ultrafast laser

Ultrafast laser welding is an emerging direct bonding technology, which has remarkable advantages of high flexibility, high precision, and wide material suitability, and has drawn considerable attention in recent years due to the potential applications in the fields of optics, healthcare, and optoelectronic. However, the quality of ultrafast laser welding is found to depend strongly on the focal position relative to sample interface and the modulation of thermomechanical response behavior of material. To relax the focusing condition, meanwhile to improve the mechanical and optical quality of ultrafast laser welding, we introduce a spatial beam shaping method to modulate the laser focal field and thermal accumulation effects under the high repetition rate regime in this work. An elongated laser focus, i.e. tailored Bessel beam is generated and is demonstrated to harvest remarkable performance in energy deposition uniformization, cavitation damage suppression, and molten region modulation. A stable glass welding with negligible stress concentration, high shear resistance, and large focal tolerance is realized.