Fabrication and laser performance of polycrystal and single crystal Nd:YAG by advanced ceramic processing

We report the first demonstration of polycrystalline Nd-doped YAG ceramics with almost perfect pore-free structure and Nd-doped YAG single crystal by advanced ceramic processing. The laser conversion efficiency of pore-free polycrystalline Nd:YAG ceramics is extremely high and its optical quality is comparable to that of commercial high quality Nd:YAG single crystal. Moreover, we have succeeded also in fabrication of Nd:YAG single crystal, which enables laser oscillation, by solid-state reaction method. Laser oscillation efficiency was very low when the pores were remained inside single crystal, however the laser oscillation efficiency of pore-free Nd:YAG single crystal was slightly higher than that of polycrystalline Nd:YAG ceramics having grain boundaries. From this fact, it was found that the optical scattering inside the Nd:YAG ceramics occurs mainly at the residual pores and the scattering at the grain boundary is very little. In addition, we confirmed that high concentration Nd:YAG single crystal can be fabricated by sintering method.