Fabrication, microstructure and laser performance of composite Nd:YAG transparent ceramics

“Sandwich” structure YAG/Nd:YAG/YAG ceramics with different core (Nd3+ doped area) lengths of 1 mm, 5 mm and doping concentrations of 1 at.%, 2 at.% were prepared by dry pressing and vacuum sintering of oxide powder mixture. Smaller average grain size was found in the specimen with the larger core and higher doping concentration. With the increase of core length, the optimum transmission of output coupler increases from 10% to 19% and better laser performance can be obtained. However, longer core length causes the noticeable thermal lens effect, which influences the beam quality significantly. It is also reflected in the thermally induced depolarized beam pattern, which becomes more obvious with the longer core length and higher Nd3+ doping concentration.