Diffusion Bonding Crystals are crystals consisting of two, three, or more parts of different materials, where the constituent parts are combined through a technique called diffusion bonding, that is, the diffusion of atoms across their interface. Diffusion Bonding Crystals are often used to decrease the thermal lens effect, which is conducive to the stability of lasers and high-power lasers. This bonding technique can not only significantly improve the laser performance and beam quality, but is also beneficial to the integration of laser systems and access to large-size crystals.