Аннотация:Refractive indices of lithium niobate crystals doped by magnesium and yttrium have been measured in the visible and IR spectral regions. Coefficients of the Sellmeier formula have been calculated which describe dispersions of the refractive indices for ordinary and extraordinary waves in the region of 0.4 - 1.1-mu-m. The method of parametric light scattering has been employed to investigate the dispersion of the crystal with the molecular concentration of the MgO admixture equal to 5% in the IR wavelength region up to 5-mu-m. Angular characteristics have been determined of frequency doublers manufactured from doped lithium niobate crystals.