Direct joining of YAG crystal and Cu by femtosecond laser

YAG crystal is successfully joined with Cu using femtosecond laser for the first time. Effective joining of 2 mm-thick YAG and Cu was achieved across a broad range of joining parameters, with laser power ranging from 50 to 150 mW and processing speed from 50 to 200 μm/s. The maximum shear strength of 34.4 MPa was obtained at 100 mW and 50 μm/s. No interfacial reactions are observed between the base materials during the joining process. Both materials are found to be modified by the femtosecond laser, forming an amorphous YAG phase on the ceramic side and fine grains at the interface region on Cu side. YAG and Cu are joined through microscopic mixing and interlocking at the interface. In addition, the effect of the laser power and processing speed on joint properties have been analyzed. The width of the weld lines and the laser-affected zone varied with different parameters, while the shear strength of the joints exhibited only minor changes. The innovative use of femtosecond laser in joining YAG and Cu is expected to realize the reliable joining of the two materials with low residual stress, offering potential applications in high-power laser systems.