Title: PARAMETRIC CRYSTAL OPTICS OF NONMAGNETIC FERROICS
Authors: O.G.Vlokh (Institute for Physical Optics, 23 Drahomanov St., UA-290005 Lviv, Ukraine)

Proceeding from the symmetry principles of crystal physics and thermodynamics we analyze parametrical optical phenomena induced by external fields of different kind and structural phase transitions in ferroelectrics and ferroelastics. Special attention is paid to the phenomena of spatial dispersion (electro- and piezogyration). A phenomenological approach to the description of these phenomena is illustrated by the most expressive experimental results obtained for the following crystals: KH$_{2(1-x)}$D$_{2x}$PO$_{4}$ (KDP, DKDP), K$_{2}$H$_{2}$AsO$_{4}$ (CDA), RbH$_{2}$PO$_{4}$ (RDP), Pb$_{5}$(Ge$_{(1-x)}$Si$_{x}\!$)$_{3}$O$_{11}\!\!$, Pb$_{3}$(PO$_{4}$)$_{2}$, K$_{2}$Cd$_{2}$(SO$_{4}$)$_{3}$, (NH$_{3}$CH$_{2}$COOH)$_{3}$H$_{2}$SO$_{4}$ (TGS), and NaKC$_{4}$H$_{4}$O$_{6}$4H$_{2}$O (RS). Apart from new effects in the crystals of the A$_{2}$BX$_{4}$ group with incommensurately modulated structure, in particular, crystals [N(CH$_{3}$)$_{4}$]$_{2}$ZnCl$_{4}$, [N(CH$_{3}$)$_{4}$]$_{2}$FeCl$_{4}$, K$_{2}$ZnCl$_{4}$, K$_{2}$ZnCl$_{4}$, Co$^{2+}$ are considered.

Key words: crystal optics, ferroelectrics, optical activity, ferroics, phase transitions
Comments: Figs. 23, Refs. 50, Tabs. 0.