LiGa0.54In0.46S2: A new infrared nonlinear optical material with large laser damage threshold designed by gallium substitution in LiInS2

Abstract Larger second-order harmonic generation (SHG) efficiency and high laser damage threshold (LDT) are two crucial requirements for the practical applications of IR nonlinear optical (NLO) materials. Li-(Ga, In)-Q2 (Q = S, Se) is a well-known IR NLO materials system, in which In Q bonds are more covalent than Ga Q bonds and benefit larger SHG efficiency. However, the incompatibility between LDT and SHG leads to a smaller LDT of LiInS2 than that of LiGaS2. A new IR NLO compound LiGa0.54In0.46S2 was successfully synthesized by the introduction of gallium in LiInS2, where mixing Ga3+ in In3+ sites result in a wider band-gap of 3.86 eV and a smaller thermal expansion anisotropy value (0.26) compared with LiInS2, leading to the large LDT of 12 times that of commercial AgGaS2 under 1064 nm at room temperature. Meanwhile, the title compound had a relatively strong SHG efficiency of about 0.6 times that of AgGaS2 under a 1910 nm laser radiation. This work highlights the strategy of pursuing IR NLO materials with high LDTs by atom doping in classic material systems.