Abstract LiInSe 2 and mixed LiIn(S 0.5Se 0.5) 2 crystals have been grown by vertical Bridgman–Stockbarger method. Optical properties of deep red LiInSe 2 and orange LiIn(S 0.5Se 0.5) 2 crystals have been evaluated. The dispersion of refractive indices has been measured and the Sellmeier coefficients have been calculated for LiInSe 2 and LiIn(S 0.5Se 0.5) 2 crystals. Linear dependence of the refractive indices on Se/(S + Se) ratio has been found in LiIn(S 1– x Se x ) 2 compounds. The ranges of phase matching possible in LiIn(S 1– x Se x ) 2 solid solutions for main crystal planes have been calculated with using Sellmeier equations specified for the compounds.