Features of the Bragg Diffraction on the Regular Domain Structures with Inclined Walls in 5% MgO:LiNbO3

The results of an experimental study and theoretical analysis of Bragg diffraction of light on regular domain structures (RDS) with inclined walls in a sample of 5% MgO:LiNbO3 at different positions of the center of an elliptical probe laser beam with a waist size of 2Δz ≈ 25 µm along the polar Z axis are presented. From the experiments it has been found that the diffraction efficiency η1(z) for the first spatial harmonic of perturbations of the optical properties created by the walls of the RDS in the crystal is characterized by nonmonotonic behavior with a minimum of η1 = 0.02 at z = 0.45 mm and two maxima: η1 = 0.11 at z = 0.19 mm and η1 = 0.15 at z = 0.80 mm. Under theoretical analysis of the diffraction efficiency at Bragg maxima we have used an approach based on the Fourier decomposition of dielectric tensor perturbations created by inclined walls of the RDS in discrete spatial harmonics with coefficients determined by the components of the continuous angular spectrum. The derived integral expressions for the diffraction field made it possible to describe the dependences of η1(z) in the Bragg diffraction maximum corresponding to a discrete harmonic with the number m = 1 in the distribution of the perturbations of the optical properties created by RDS with different domain wall parameters. Numerical calculations carried out within the framework of the developed model demonstrated a satisfactory agreement of the theoretical dependence of η1(z) with the relevant experimental data.