Synergically Assembling Advantageous Groups toward High-Performance Infrared Nonlinear Optical Materials AIICdSiSe4 (AII = Sr, Ba)

Developing superior infrared nonlinear optical (IR NLO) materials with broad bandgap (E_g) and large NLO response is an urgent need for the highly expected mid-/far-IR solid-state lasers, but challenging due to the contradiction between the critical parameters. Herein, guided by the short board effect of E_g and longboard effect of NLO response, four new IR NLO candidates A^IIB^IISiSe₄ (A^II = Sr, Ba; B^II = Cd, Hg) derived from the centrosymmetric (CS) SrIn₂Se₄, with a structural transition from Ama2 (A^IIHgSiSe₄ and SrCdSiSe₄) to Fdd2 (BaCdSiSe₄), are rationally designed and fabricated by synergically assembling advantageous structural groups. Among them, A^IICdSiSe₄ displays the optimal comprehensive performance in the known A^IIB^IIC^IVSe₄ family compounds, including a strong NLO response (≈2.1–2.7 × AgGaS₂), a wide selenide E_g (≈2.67–2.78 eV) and a high laser-induced damage threshold (≈4.0 × AgGaS₂). Theoretical investigations uncover that the superior properties in the compounds can be contributed to the synergic-assembly of advantageous [A^IISe₈], [CdSe₄], and [SiSe₄] units. The results enrich the chemical and structural diversities of chalcogenides, and open an avenue for the design of high-performance IR NLO materials from the known CS compound by the aliovalent group substitution and synergically assembling strategy.