ELECTRONIC EFFECTS OF SUBSTITUTION CHEMISTRY IN THE KTIOPO4 STRUCTURE FIELD - STRUCTURE AND OPTICAL-PROPERTIES OF POTASSIUM VANADYL PHOSPHATE

Potassium titanyl phosphate (KTP) is a remarkable nonlinear optic/electrooptic material whose crystal structure permits the facile substitution of many isovalent ions for K, Ti, and P. Subtle structural and electronic influences result, sometimes causing dramatic changes in NLO properties. Replacing Ti with V yields potassium vanadyl phosphate (KVP), which is structurally very similar to KTP but nearly opaque in the visible region due to the decreased energy of the vanadium dπ charge-transfer band. KVOPO4 is orthorhombic, space group Pna21, with a = 12.816 (5) Å, b = 6.388 (2) Å, and c = 10.556 (5) Å. There are two KVOPO4 units per asymmetric unit, and Z = 8. Optical absorption at 532 nm inhibits SHG intensity in KVP if 1.064-μm radiation is used as the pump source. The anionic group model was extended to predict the contribution to βijk from the d electron in KVP, and it is concluded that t2g occupancy should not affect optical nonlinearity. The electronic influence of the K+ ion on the mixing coefficient of valence and charge-transfer bands is less significant in KTP and KVP than is the analogous cation-framework interaction in AgTiOPO4 and β-NaTiOPO4, in which this influence results in a diminished NLO response. © 1990, American Chemical Society. All rights reserved.