Bo Yang

Ultrashort pulse laser (USPL) with its excellent properties of ultrashort pulse width and extremely high peak power is widely applied in precision machining, microfabrication, and biomedicine. In recent years, there is a growing trend in using USPL in the field of welding. This emerging welding technology is primarily applied to the welding of transparent materials. By focusing USPL at the welding interface, laser energy transfers to substrates within a narrow area through the nonlinear absorption process, accompanied with large amount of heat release to achieve the melting and bonding. Due to the extremely short pulse width and limited energy input, thermal diffusion around the joint is minimal, resulting in the diminished welding region, lower thermal stress, and enhanced welding precision. This method holds significant promise for welding samples with a large coefficient of thermal expansion (CTE) difference. In this review, the welding of transparent materials is first introduced, including the welding process, mechanism, and process optimization. Following this, the welding of transparent materials‐opaque materials and opaque materials‐opaque materials are described. The current progress in the applications of USPL welding is then presented. Finally, the development prospects of USPL welding technology are summarized and discussed.