A novel promising infrared nonlinear optical selenide KAg₃Ga₈Se₁₄ designed from benchmark AgGaQ₂ (Q = S, Se)

Obtaining fresh nonlinear optical (NLO) materials is an attractive and challenging topic for the development of laser techniques. Using benchmark AgGaQ2 (Q = S, Se) as the template, new KAg3Ga8Se14 is obtained by a solid-state reaction. Its structure can be built by the intergrowth of 2 : 1 AgGaSe2 and Ga2Se3-like slabs if the K site is occupied by Ag. Powdery KAg3Ga8Se14 demonstrates moderate phase-matchable NLO responses, and a LDT of ca. 2 × AgGaS2. DFT calculations reveal that both AgSe4 and GaSe4 tetrahedral motifs contribute a lot to the NLO performance. This work reveals a new class of promising infrared NLO materials, and the design strategy may apply to other systems.