Linear and nonlinear optical properties of LiInS2

LiInS₂ is an $A^{\mathrm{I}}{B}^{\mathrm{III}}{C}_2^{\mathrm{VI}}$ ternary semiconductor crystallizing with mm2 symmetry. The useful transparency range is 0.5–8 μ, over which we have measured the refractive indices. The optical nonlinear coefficients for second harmonic generation have also been measured. The nonlinear figure of merit is comparable to that of AgGaS₂. Three‐frequency collinear phase matching is possible in LiInS₂ and is analyzed in some detail. LiInS₂ is judged to be a potentially more useful optical nonlinear material than the analogous compound LiGaO₂.