Nonlinear absorption in crystalline niobates containing stimulated defects

The authors have examined Ba/sub 2/NaNb/sub 5/O/sub 15/ and LiNbO/sub 3/ crystals, which are widely used in laser instrumentation, which had radiation-stimulated defects. The defects were produced with a ..gamma..-Co/sup 60/ apparatus at room temperature with absorbed doses of 1 x 10/sup 5/-2 x 10/sup 8/ rad; the Ba/sub 2/NaNb/sub 5/O/sub 15/ and LiNbO/sub 3/ crystals were irradiated at dose rates of 2.4 x 10/sup 4/ and 8.0 x 10/sup 4/ rad/min, correspondingly. The optical absorption was recorded with a Beckman Acta MVII spectrophotometer at 200-1400 nm before and after irradiation.