三元AGa_(5)S_(8)(A=K,Rb,Cs):通过“一替多取代”策略制备的红外非线性光学材料

Ternary AGa_(5)S_(8)(A=K,Rb,Cs):Promising infrared nonlinear optical materials rationally realized by“one-for-multiple substitution”strategy

目前,商用的红外非线性光学晶体材料,如具有类金刚石结构的硫属化合物AgGaQ_(2)(Q=S,Se),具有强的非线性光学系数.然而,相对较低的抗激光损伤阈值制约了其在高能激光领域的应用.以类金刚石结构的闪锌矿ZnS为模板,我们通过“一替多取代”策略,即[SZn_(4)^(6+)+5Zn^(2+)■A^(+)+5Ga^(3+)](A=K、Rb和Cs),采用固相合成方法,获得了三元晶体AGa_(5)S_(8)(A=K、Rb和Cs).极性结构的AGa_(5)S_(8)保持了类金刚石阴离子骨架框架,非线性光学功能基元GaS4四面体以平行排列的方式堆积,使其具有高的相位匹配倍频强度(1.1–1.2×AgGaS_(2));另外,含有高正电性A+阳离子使其表现出3.10–3.37 eV的宽带隙,进而提高抗激光损伤阈值(9.3–12.4×AgGaS_(2)).晶体AGa_(5)S_(8)(A=K、Rb和Cs)是第一个具有大倍频响应(≥1.0×AgGaS_(2))和宽带隙(≥3.0 eV)的三元含碱金属的硫属化合物,满足了优秀红外非线性光学材料的严格要求.此外,“一替多取代”策略在类金刚石结构演变中具有重要意义,并为获得新非线性光学材料提供了良好的机遇.

Commercially available infrared(IR)nonlinear optical(NLO)materials,such as diamond-like AgGaQ_(2)(Q=S,Se),display large NLO coefficients but relatively low laserinduced damage thresholds(LIDTs),which seriously hinder their widespread laser applications.Herein,the“one-for-multiple substitution”strategy,namely,[SZn_(4)^(6+)+5Zn^(2+)■A^(+)+5Ga^(3+)](A=K,Rb and Cs),is applied on the diamond-like zinc-blende ZnS,and affords three new polar ternary crystals AGa_(5)S_(8)(A=K,Rb and Cs)through the solid-state method.These compounds inherit the diamond-like anionic backbone framework in ZnS where the NLO functional motifs GaS4are arranged in a parallel manner.This characteristic accounts for the remarkable phase-matchable second-harmonic generation intensities(1.1-1.2×AgGaS_(2)).In addition,the inclusion of the highly electropositive A+cations affords a band gap ranging from 3.10 to 3.37 eV,which facilitates the improvement of LIDT(9.3-12.4×AgGaS_(2)).To the best our knowledge,crystals AGa_(5)S_(8)(A=K,Rb and Cs)are the first series of ternary A-inclusion chalcogenides with large second-harmonic generation responses(≥1.0×AgGaS_(2))and wide band gaps(≥3.0 eV),fulfilling the rigorous requirements of outstanding IR NLO materials.In addition,the“one-for-multiple substitution”strategy presents the great significance of diamondlike structure evolution and provides a remarkable opportunity to achieve NLO materials.