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535.36:548Comparative studies are made of the photorefractive scattering of light in nonlinear single crystals of lithium niobate with congruent compositions (LiNbO 3 ) doped with "photorefractive" Cu [0.015 mass %] and "nonphotorefractive" Zn [0.5 mass %] cations. For the first time it is found that single crystals doped with "photorefractive" and "nonphotorefractive" cations have different indicatrices for photorefractive light scattering. The aperture angle for photorefractive scattering reaches its steady state value more rapidly with high laser powers than with low. However, at high powers laser induced heating of the crystal is greater, and this leads to a narrowing of the scattering indicatrix. It is also found that photorefractive scattering in these single crystals depends on the region of the boule from which a sample has been cut. This indicates that there is a nonuniform distribution over the boule of the imperfections with localized electrons which determine the magnitude of the photorefractive effect.Introduction. Photorefractive recording of phase lattices, which is used for long-term memory and the creation of high selectivity devices for holographic recording, is currently far from perfection and is in a developmental stage [1,2]. To a significant extent this is because of a lack of optimal photorefractive single crystal materials [2]. One of the most promising materials for holographic information recording is single crystal lithium niobate (LiNbO 3 ), whose photorefractive properties can be varied over a wide range by varying the stoichiometry (the ratio R = Li/Nb) and doping [2][3][4][5]. Single crystals with a high photorefractive efficiency can be obtained by doping the lithium niobate structure with transition metal cations (Fe, Cu, Mn, Ni, etc.; "photorefractive" cations

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