Crystal Growth and Electro-Optic Effect of Bismuth Germanate, Bi4 (GeO4)3

Single crystals of bismuth germanate Bi4(GeO4)3 having the eulytine structure, space group Td6, were grown. They were crucible-free pulled from a pool of molten material produced in its own powder at 1040°C by a thermal imaging technique. The material has an index of refraction of 2.07 and transmits light between 0.4 and 6.0 μ. The electro-optic coefficient r41 was determined to be 1.03·10−10cm/V. Although materials with higher r41 values are known, Bi4(GeO4)3 may find applications because the growth of large crystals appears possible by classical pulling techniques. A large variety of chemical substitutions are possible in the eulytine structure and might lead to improvements in the magnitude of r41.