Linear and nonlinear optical properties of some ternary selenides

The refractive indices of the ternary
A^{I}B^{III}C_{2}^{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.