Comparison of Acoustic and Nonlinear Optic Properties of Strontium Barium Niobate Crystals of Different Compositions

Abstract

abstractBrillouin spectra and generation of the second optical harmonic in a series of SBN-x crystals with different chemical compositions are investigated in the 115–850 K temperature range. The integral intensity of the second harmonic signal follows the Arrhenius law with activation energies of ΔU = 0.09–0.3 eV. The second harmonic generation (SHG) is observed in paraelectric phase of the SBN-x crystals, revealing the presence of polar regions in the paraelectric phase. The spectral width of the SHG spectrum does not exceed 0.3 cm−1 and is temperature independent. Upper limit of the spectral width of the SHG spectrum provides lower limit of the lifetimes of polar regions, which are longer than 15 ps. It suggests that the doubled frequency signal in the paraelectric phase of the SBN-x crystals is generated in areas with lifetimes longer than 15 ps. It is shown that local polar regions cannot explain the anomalies of the elastic module near the ferroelectric phase transition in SBN-x.