Dispersion of electrogyration in sillenite crystals

In this paper we report on the dispersion of the electrogyration of the sillenite crystals Bi₁₂SiO₂₀, Bi₁₂GeO₂₀, and Bi₁₂TiO₂₀ over the visible spectrum. We measure the electrogyration coefficient from the rotation of the polarization plane of the transmitted beam due to the externally applied electric field. Both light transmission and electric field direction are parallel to the [111] crystallographic direction in which the influence of the electrooptic effect is diminished. In all cases the electrogyratory coefficient is found to be between 0.5–3.75×10^-13 m/V and has the same dispersion pattern like optical activity and refractive index. PACS 78.20.Ek; 78.20.Jq; 42.70.Nq