Secondary structure and optical properties of ferroelectric lithium niobate crystals

Manifestation of the secondary structure of lithium niobate single crystals with low photorefractive effect was researched by Raman scattering and photoinduced light scattering (PILS). Laser induced static microdefects with changed refractive index were revealed. Shape and asymmetry of PILS patterns were demonstrated to depend on difference in refractive indexes and energies of ordinary and extraordinary beams. Nonmonotonicity of temperature dependence of Raman bands intensities was shown to be caused by gradual shutdown of photorefraction mechanisms at rise in the temperature that leads to decrease of laser radiation intensity. We have revealed an concentration area of high structure order in LiNbO3: Zn crystals. Raman bands that probably correspond toA(2) symmetry scalar vibrations were detected in LiNbO3 crystals strongly doped by Zn and Mg.