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.