Thermodynamic analysis of electro-optic coefficients of ferroelectrics

The electro-optic coefficients of ferroelectric materials were obtained by Landau thermodynamic theory. It is proved that if the permittivity tensor is diagonal, then some ratios of the electro-optical coefficients are equal to the ratios of its diagonal components. The dependence of electro-optic coefficients on the external electric field for single-crystal barium titanate was studied and discussed. It is shown that electro-optic coefficients are rather high for barium titanate due to a non-linear response of dielectric susceptibility to electric field strength.