Characterization of photorefractive BCT:Rh crystals at 1.06 μm by two-wave mixing

We present an experimental investigation of the photorefractive properties of rhodium-doped barium calcium titanate (BCT) crystals of the congruent melting composition Ba0.77Ca0.23TiO3. Considering the results previously obtained on these crystals in the visible region and at 850 nm wavelength, it should be a good alternative to BaTiO3:Rh. Besides, the rhodium doping has the effect of making this material sensitive up to the wavelength of 1.06 mum-a very technologically significant wavelength, because of the existence of high-power lasers. Therefore we present a study of rhodium-doped BCT crystals at 1.06 mum. These crystals are characterized by two-wave-mixing experiments. Two-beam coupling gain factors of up to 7.5 cm(-1) with ordinary polarization and a response time of the order of 1 s at an incident power of 10 W cm(-2), have been obtained. All properties are explained by a three-centre charge transport model, together with the existence of an iron impurity which masks the influence of rhodium at low doping concentrations.