Superior Infrared Nonlinear Optical Performance Achieved by Synergetic Functional Motif and Vacancy Site Modulations

Achieving large phase-matchable (PM) nonlinear optical (NLO) efficiency and high laser-induced damage threshold (LIDT) in an infrared second-order NLO (IR NLO) material is the most crucial technical endeavor but the most challenging. A synergetic strategy of modulating NLO functional motifs and vacancy sites for excellent comprehensive performances is proposed. The application of such a strategy in salt-inclusion systems affords two chalcogenides [K₄Cl]­[CdGa₉Q₁₆] (Q = S, 1; Se, 2), which possess the important merits of a practical IR NLO material, including large PM NLO efficiency (0.9 and 2.4 × AgGaS₂) and high LIDTs (22.6 and 7.7 × AgGaS₂). Remarkably, compound 2 has the strongest SHG intensity among all known PM salt-inclusion chalcogenides. In addition, the strategy also enhances the structural anisotropy and renders 2 the first PM one among all known NLO salt-inclusion selenides. This work provides a novel design approach of the IR NLO material much more superior than other unique modulations.