Linear and nonlinear optical properties of some ternary selenides

The refractive indices of the ternary A^IB^IIIC₂^VI semiconductors CuAlSe 2, AgGaSe 2, CuGaSe 2, and AgInSe 2 have been measured over most of the transparency range of these crystals. The optical nonlinear coefficients for second-harmonic generation of AgGaSe 2 CuGaSe 2, and AgInSe 2 have also been measured. Three-frequency colinear phase matching is analyzed in detail for AgGaSe 2. The birefringences of the other three crystals are not sufficient to permit three-frequency colinear phase matching within the range of the measured index. The merits of AgGaSe 2 for nonlinear optical applications are evaluated in comparison with other promising infrared nonlinear materials.