ELECTROOPTIC AND PHOTOREFRACTIVE PROPERTIES OF FERROELECTRIC BARIUM-CALCIUM TITANATE CRYSTALS

Barium-calcium titanate of congruently melting composition Ba0.77Ca0.2 3TiO3 is a novel photorefractive crystal. The refractive, electrooptic and photorefractive properties of an undoped as grown sample are inve stigated: The refractive indices are slightly smaller than those of Ba TiO3, but the electrooptic coefficients r(113) = 36 +/- 3 pm V-1 and r (333) = 140 +/- 5 pm V-1 (light wavelength 514.5 nm) are larger. Light -induced absorption and a sublinear photoconductivity indicate the par ticipation of a shallow level in the charge transport. There are no sp ace charge limiting effects; bulk photovoltaic fields of the order of 15 kV m(-1) are present. The obtained two-beam coupling gain coefficie nts for ordinarily and extraordinarily polarized light are 160 m(-1) a nd 425 m(-1), respectively. In summary, barium-calcium titanate is a v ery promising crystal which will compete with barium titanate.