GROWTH OF SINGLE-CRYSTAL PHOTOREFRACTIVE FIBERS OF BI12SIO20 AND BI12TIO20 BY THE LASER-HEATED PEDESTAL GROWTH METHOD

Photorefractive single-crystal fibers of Bi12SiO20 up to 90 mm in leng th and Bi12TiO20 up to 50 mm in length with diameters of 650-1200 mum were grown by the laser-heated pedestal growth (LHPG) method. Both Bi1 2SiO20 and Bi12TiO20 fibers were pulled from stoichiometric (6:1) melt s at pulling rates of 0.3 and 0.2 mm/min, respectively, the feeding ra te was 0.1 mm/min. Growth conditions, morphology and chemical composit ion of the grown fibers were studied. The possible mechanisms of cryst allization of incongruently melting Bi12TiO20 fiber from the stoichiom etric melt were discussed. The energy-exchange effect was observed in the BSO fibers at the wavelength lambda = 0.5145 mum.