LiInS2: A new nonlinear crystal for the mid-IR

Second harmonic generation for fundamental wavelengths between 2.3 and 6 μm and optical parametric generation from 5 to 12 μm in the mid-IR are demonstrated in a new nonlinear crystal, LiInS₂, exhibiting no two-photon absorption near 800 nm. Photoinduced absorption in the visible to near-IR occurring at λ<450 nm excitation can be removed with illumination at λ>500 nm or minimized by annealing in In₂S₃ vapor.