LiAlS2: A promising infrared frequency-conversion material with ultrawide band gap and high laser-induced damage threshold

The development of infrared (IR) nonlinear optical (NLO) crystals could foster their wide applications in civil and military fields. Thus, IR NLO materials with a band gap, high laser-induced damage threshold, lack two-photon absorption are urgently needed. This work reports the comprehensive properties LiAlS2 through systematic experimental characterizations first principle study. results confirmed congruently melting feature LiAlS2, type-I phase matching (PM) performance, its second-harmonic generation (SHG) response (0.2 × AgGaS2 at 2.09 µm). Notably, shows widest gap 5.13 eV among selected an ultrahigh threshold about 28 times that AgGaS2. structure-property relationship analysis indicates [AlS4] tetrahedra determine primarily contribute to SHG response. Moreover, calculated effective coefficient deff, refractive index dispersion relation, shortest PM wavelength reported. this study indicate can be promising material high-energy laser systems.