Two-in-one: assembling hybrid supertetrahedra chromophores and achieving high-performance “hexagonal warriors” in nonlinear optical crystals

Nonlinear optical (NLO) crystals capable of controlling and manipulating light to generate coherent radiation at a variety of difficult-to-access wavelengths are essentially crucial for many high-tech applications, yet the rational design of NLO crystals with high-performance remains a great challenge. Herein, inspired by two facts, namely, hetero-anionic structures can effectively integrate the diverse property superiorities of single-anions, and T2-type supertetrahedra can exhibit enhanced polarizability compared to simple tetrahedra. We assembled multiple different [TS 4 ] (T = Zn, Sn) tetrahedra to form the hybrid T2-type supertetrahedra and successfully synthesized new hybrid T2-type supertetrahedral IR NLO crystals, Ae 5 Zn 3 Ga 2 Sn 2 S 15 (Ae = Sr and Ba), both of which exhibit intriguing NLO properties, including strong second harmonic generation responses (2.8 × AgGaS 2 –3.0 × AgGaS 2 ), wide band-gaps (2.81–2.89 eV), high laser-induced damage thresholds (∼15 × AgGaS 2 ), a broad IR transmission range (up to 14 µm), and suitable birefringence (0.048–0.051@1064 nm). More significantly, both exhibit congruent melting behavior, and a high-quality single crystal of Ba 5 Zn 3 Ga 2 Sn 2 S 15 with centimeter-level has been successfully grown using the Bridgman method. These findings strongly suggest that Ba 5 Zn 3 Ga 2 Sn 2 S 15 holds great promise as an IR NLO crystal, and the strategy for constructing hybrid T2-type supertetrahedra is effective for designing novel high-performance NLO crystals.