The optical activity of crystals induced by an electric field (electrogyration)

Abstract

The author makes an analysis of symmetry in respect of the effects associated with rotation of the polarization plane of light in crystals, namely, the optical activity (symmetry ∞), magnetic rotation (symmetry ∞/m; Faraday effect), and polar optical activity effect (symmetry ∞mm; antisymmetric part of the second-rank axial tensor). The latter effect is being predicted. Using tables of irreducible representations of the point symmetry groups with geometrized bases, including the invariants described by second-rank axial tensors, the author analyses the phase transitions induced solely by optical activity (symmetry ∞2; 14 cases) and optical activity coupled with spontaneous polarization (symmetry ∞mm; 16 cases). A review is given of the work on electrogyration effects (spontaneous and forced), which consist in optical activity induced by an electric field (axial tensors of the third and fourth ranks). There is a discussion of the features of electrogyration during phase transitions in Rochelle salt, triglycine sulphate and lead germanate. The results of measurement of the electrogyration coefficients are given for the crystals α-H|O3, L|IO3 and PbMoO4.