Preparation and Characterization of the Composite Nd:YAG/Nd:YAG Crystals

Composite crystals can not only improve the heat management of high-average-power laser considerably to obtain the high-optical-quality laser, but also be used to prepare larger size crystals. The composite Nd:YAG/Nd:YAG crystals with the size of 50 mm x 15 mm x 24 mm are prepared by thermal bonding technique using alumina balls as the pressure transfer medium. Thermal bonding experiments are carried out under different heat treatment processes and sintering atmosphere, and the quality of the composite crystals is characterized by transmittance, extinction ratio, bonding strength, and laser properties. The results show that alumina ball as pressure transfer medium and vacuum sintering atmosphere can effectively improve the uniformity of pressure on the bonded crystals, which is beneficial to overcome the pressure inhomogeneity, reduce the bubble or hole, cracks and other defects in the bond interface, and the bonded crystal optical quality is improved considerably. The laser performance of the composite crystals pumped by laser diode is compared with single crystal and they have the same laser slope efficiency, which indicates that the thermal bond technique with alumina balls used as pressure transfer medium and vacuum sintering is a successful method to obtain high-quality composite laser crystals.