Light-induced charge-transport properties of photorefractive barium-calcium-titanate crystals doped with rhodium

Nominally pure and rhodium-doped barium-calcium-titanate crystals of the congruently melting composition Ba0.77Ca0.23TiO3 (BCT) are grown by the Czochralski technique. These crystals are characterized by holographic and conventional electrical experiments. The doped samples have an absorption maximum at 630 nm. They are hole conductive, and for intensities between 0.1 and 1 W cm(-2) all properties are explained within a one-center charge-transport model. Two-beam-coupling gain factors up to 8 cm(-1) are obtained, and doping with rhodium increases the effective trap density. Although diffusion is the dominant charge-driving force, bulk photovoltaic currents also occur which are especially pronounced in the range between 460 and 640 nm.