Radiation defects in single crystals of KTiOPO/sub 4/

Single crystals of KTiOPO/sub 4/ (KTP) are a promising nonlinear optics material having high nonlinearity coefficients comparable in magnitude with analogous coefficients for Ba/sub 2/NaNb/sub 5/O/sub 15/. In the initial KTP crystals, using the EPR method, they detected paramagnetic Fe/sup 3 +/ impurities and other ions giving a complex multi-line spectrum over a wide field range (up to 7000 Oe). After ..gamma..-irradiation, the single crystal takes on a cream color. The induced optical absorption spectrum, represented by a broad band with weakly resolved maxima in the 490 and 550 nm region, has significant anisotropy. The intensity, shape, and position of the bands in the extrinsic absorption spectrum vary with a change in orientation of the crystal relative to the probe beam of the spectrophotometer. Simultaneously with induced absorption in the optical spectrum, two groups of high-field and low-field lines appear in the EPR spectrum in the g = 2 region. The high-field signal has a complex structure, changing with the orientation of the crystal in the resonant cavity, and also has a weak anisotropy in the g-factor and hyperfine coupling constants.