Nonlinear optical properties of ferroelectrics Sr2Nb2O7 and La2Ti2O7 with stratified structure

Quadratic optical susceptibility and photorefraction properties of ferroelectric crystals produced by the Czochralsky method have been studied. Large crystals grow in the monodomen state and do not stand in need of additional polarization, they are transparent from 0.33 μk. The lengths values of coherent interaction, and coefficients of quadratic susceptibility have been obtained by the analysis of orientation dependence of the second harmonic intensity. The signs of nonlinear coefficients are determined from the condition of the best agreement of the Jerphagnon nonlinear vector value and spontaneous polarization value. Phase synchronism during the second harmonic generation in the Sr2Nb2O7 case has been detected. The Sr2Nb2O7 and La2Ti2O7 crystals have a significant photoconductivity