Phase Matchability Transformation in the Infrared Nonlinear Optical Materials with Diamond‐Like Frameworks

Phase matchability is a prerequisite for infrared nonlinear optical (IR‐NLO) crystals. Hitherto, it is relatively infrequent to design and synthesize phase‐matching (PM) materials from known non‐phase‐matching (NPM) materials. This work reports a series of PM chalcogenides AMII3Ga5S11 (A = K, Rb, Cs; MII = Cd, Mn) with diamond‐like frameworks (DLFs), which are derived from the known NPM AMII4Ga5S12 in the A2S−MIIS−Ga2S3 pseudoternary diagram. Notably, ACd3Ga5S11 and AMn3Ga5S11 are isomeric and exhibit different DLFs and remarkable overall properties. Especially, KCd3Ga5S11 achieves the coexistence of wide band gap (Eg = 3.25 eV), strong second‐harmonic‐generation (SHG) response (1.7 × benchmark AgGaS2) and ultrahigh laser‐induced damage threshold (36.5 × benchmark AgGaS2), which is the best IR‐NLO chalcogenides with DLF known to date. Theoretical calculations reveal that their superior performance and PM behavior are benefited from the anisotropic structural characteristics, i.e., DLFs. This work demonstrates the feasibility of designing PM IR‐NLO materials via the partial removal of asymmetric building blocks in DLF structures of NPM materials that is accessible and controllable by chemistry means. A series of novel infrared nonlinear optical (IR‐NLO) materials with excellent performances are designed and the change from a non‐phase‐matching (NPM) parent compound AMII4Ga5S12 to the phase‐matching (PM) AMII3Ga5S11 is observed. This interesting phase matchability transformation in diamond‐like frameworks is ascribed to the partial removal of asymmetric building blocks.