Optical Scattering Centers in Polycrystalline Nd:YAG Laser

For the present study, 1.1-at.%-Nd-doped YAG ceramics with controlled amounts of grain-boundary phase were fabricated by a solid-state reaction method using high-purity powders. The optical scattering loss of the Nd:YAG ceramics, obtained from Fresnels equation, increased simply with increased amounts of grain-boundary phase. The continuouswave laser output power of the Nd:YAG ceramics clearly was related to the scattering loss coefficients of the specimens that, in turn, were affected by the amount of grain-boundary phase. Although the scattering loss coefficients of Nd:YAG ceramics with grain-boundary-free structure and a lower pore volume (}150 vol ppm) were almost equivalent to those of a 0.9-at.%-Nd-doped YAG single crystal grown by the Czochralski method, the laser output power of the Nd:YAG ceramics exceeded that of the Nd:YAG single crystal with increased exciting power under excitation with an 808 nm diode laser because of the large amount of neodymium additives. Lasing performance was not affected by the existence of grain boundaries in the polycrystalline specimen.