FEATURES OF THE DEFECT STRUCTURE OF A LiNbO3:Cu(0.015 WT.%) SINGLE CRYSTAL

By direct alloying of melt with copper oxide,. compositionally uniformity LiNbO3:Cu (0,015 wt%) single crystal doped with a photovoltaically active copper dopant has been grown. The optical properties of the single crystal have been studied by photoinduced light scattering. The values of the diffusion and photovoltaic fields were calculated for the studied crystals based on the intensity and magnitude of the opening angle of the speckle structure of the photoinduced light scattering. Significant differences in the photoinduced light scattering patterns and in the values of the photoinduced light scattering photoelectric parameters of nominally pure crystals of congruent and stoichiometric compositions and a LiNbO3:Cu (0,015 wt%) crystal have been found. It has been established that when a congruent lithium niobate crystal is doped with copper cations, the diffusion field increases, the photofoltaic field decreases, and the band gap in the crystal decreases noticeably. In contrast to the crystal of stoichiometric compositions, the photovoltaic mechanism remains the predominant mechanism of photorefraction for crystals of congruent composition and LiNbO3:Cu (0,015 wt%). Photoinduced light scattering data indicate the presence of a LiNbO3:Cu(0,015 wt.%) crystal in the band gap high density of small energy levels that increase the effect of photorefraction and electrical conductivity of the crystal.