GROWTH OF LARGE DOPED BI12SIO20 CRYSTALS

The conditions for growing Cr-, Mn-, Fe-, Co-, Ni-, and Cr+Al-doped BS O crystals from a stoichiometric melt by the Czochralski method have b een the subject of research. A decrease of the absorption coefficient along the growth axis was observed in undoped crystals of 50 mm diamet er and 150 mm long, which is indicative of melt stoichiometry change i n the course of the growth run. The transmission and reflection spectr a of different crystals were measured and the absorption coefficients was determined in the range 0.38-0.70 mum. When Fe dopant concentratio n exceeds a limit value, the absorption spectrum is blue-shifted relat ive to the undoped case and the absorption coefficient decreases. Co. Cr, Mn, and Cr + Al dopants produce a red shift and increase the absor ption coefficient. Combined Cr+Al doping shift the absorption spectrum to the blue region as compared to Cr-only doping with the same Cr con centration.