Abstract
Measured quantum efficiencies of ten different Nd:YAG crystals show a variation from 0.47 to 0.87. In phototropic crystals, the quantum efficiency can 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 Nd/sup 3+/ fluorescence quenching centers. Fluorescence rates, nonequivalent crystal field (NCF) effects, line broadening, Nd/sup +3/ lattice-defect interactions, and their temperature dependences are studied. Nd/sup 3+/ site perturbations occur in all crystal samples. Five NCF Nd/sup 3+/ sites show 6 cm/sup -1/ site-to-site Stark level shifts at liquid helium temperatures. Smaller scale shifts are characteristic of particular samples. While the crystals examined show individual differences, only hydroxyl-related coloration provides specific evidence of quenching centers. >
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