Nd:YAG quantum efficiency and related radiative properties

Measured quantum efficiencies of ten different Nd:YAG crystals show a variation from 0.47 to 0.87. In phototropic crystals, the quantum efficiency may be degraded by color center formation or improved by bleaching. Color center bleaching occurs by oxidation using a high-temperature reactive atmosphere process to control crystal defects related to hydroxyl impurities. Ion-ion and ion-lattice interaction effects are examined for further evidence of Nd3+ fluorescence quenching centers. Fluorescence rates, nonequivalent crystal field (NCF) effects, line broadening, Nd3+ lattice-defect interactions, and their temperature dependencies are studied. Nd3+ site perturbations occur in all crystal samples. Five NCF nd3+ sites show 6 cm-1 site-to-site Stark level shifts at liquid helium temperatures. Smaller scale shifts are characteristic of particular samples. While the crystals examined can show individual differences, only hydroxyl-related coloration provides specific evidence of quenching centers