The complete set of material parameters of a top-seeded solution-grown ${\mathrm{BaTiO}}_3$ crystal has been determined by numerically evaluating available measurements and using additional measurements presented in this work. The parameters were determined at room temperature and consist of the low-frequency clamped dielectric constants ${\mathrm{\epsilon }}_{\mathit{i}\mathit{j}}^{\mathit{S}}$, elastic stiffness constants at constant electric field ${\mathit{c}}_{\mathit{i}\mathit{j}\mathit{k}\mathit{l}}^{\mathit{E}}$, piezoelectric stress coefficients ${\mathit{e}}_{\mathit{i}\mathit{j}\mathit{k}}$, elasto-optic tensor at constant electric field ${\mathit{p}}_{\mathit{i}\mathit{j}\mathit{k}\mathit{l}}^{\mathit{E}}$, and clamped electro-optic coefficients ${\mathit{r}}_{\mathit{i}\mathit{j}\mathit{k}}^{\mathit{S}}$.

The elastic, piezoelectric, dielectric, elasto‐optic, and electro‐optic tensors have been determined by numerically evaluating the measurements published until now and using the additional measurements presented in this work. The dependence of the speed of two elastic waves on the applied electric field is measured yielding one electroelastic constant g₁₃₁₃₃=(95±10)NV⁻¹ m⁻¹. The complete set of parameters consisting of the low‐frequency clamped dielectric constants ε^S_ij, refractive indices, elastic stiffness constants at constant electric field C^E_ijkl, piezoelectric coefficients e_ijk, elasto‐optic tensor at constant electric field p^E_ijkl, and clamped electro‐optic coefficients r^S_ijk is used to calculate effective electro‐optic coefficients and effective dielectric constants that have to be used in photorefractive experiments where the elastic deformations associated with a periodic space‐charge field have to be considered.

The coupled wave theory of Kogelnik [H. Kogelnik, Bell Syst. Tech. J. 48, 2909 (1969)] is extended to the case of moderately absorbing thick anisotropic materials with grating vector and medium boundaries arbitrarily oriented with respect to the main axes of the optical indicatrix. Dielectric and absorption modulation with common grating vector and of arbitrary relative phase shift is considered. Solutions for the wave amplitudes, diffraction efficiencies, and angular mismatch sensitivities are given in transmission and reflection geometries. The main difference of the new results with respect to the expressions valid for isotropic media arise due to the walk-off between the wave-front and energy propagation directions. The difference is particularly important in materials with large birefringence, such as organic crystals, ordered polymers, and liquid crystalline cells. The special case of Bragg diffraction and two-beam coupling at holograms recorded in optically inactive photorefractive crystals is analyzed in detail. It is found that the two-beam coupling gain is influenced substantially by an absorption anisotropy.

We relate the linear electro‐optic coefficients to the quadratic polarization‐optic and the elasto‐optic tensors by analyzing the dielectric phenomena driven by the spontaneous and induced polarization as well as the mechanical effects given by the deformation of the crystals. We determine the temperature dependence and the wavelength dispersion of the electro‐optic tensor in all the ferroelectric phases from a smaller set of data: the quadratic polarization‐optic tensor of the cubic phase, the dielectric permittivity, and the spontaneous polarization. Under the assumption that the elasto‐optic tensor at constant polarization is constant, the elasto‐optic coefficients at constant electric field in the ferroelectric phases are derived. Numerical evaluations of these coefficients for two perovskite crystals KNbO₃ and BaTiO₃ are presented. Modifications of the electro‐optic properties in doped crystals, mainly due to a change of the dielectric permittivity, are discussed as well.

We show both theoretically and experimentally that the combined processes of optical rectification and the linear electro-optic effect lead to an effective nonlinear refractive index $n_2$ in noncentrosymmetric materials. This cascaded second-order nonlinear optical effect arises in addition to the well-known contribution due to second-harmonic generation and difference-frequency mixing and is of comparable magnitude. However, it has the advantage of a broad acceptance angle because no precise phase matching is needed. Experimental results in KNb${\mathrm{O}}_3$ crystals are presented.