Highly polarized [GeOTe3] motif-driven structural order promotion and an enhanced second harmonic generation response in the new nonlinear optical oxytelluride Ba3Ge2O4Te3

Abstract

The hybrid anion strategy has been illustrated to be an effective way to design and synthesize high-performance nonlinear optical (NLO) crystals. Herein, a new NLO-active oxytelluride with a highly polarized [GeOTe₃] unit, Ba₃Ge₂O₄Te₃, has been successfully synthesized. Driven by the distorted [GeOTe₃] motif, this compound exhibits interesting structural order promotion with its parent model Ba₂ZnGe₂O₇ (BZGO). Moreover, on the basis of inheriting the polarization structure of BZGO, the Ba₃Ge₂O₄Te crystal possesses an enhanced second harmonic generation (SHG) response benefiting from the partial replacement of O with the more polarized Te. Remarkably, the experimental results and theoretical calculations reveal that Ba₃Ge₂O₄Te₃ has the potential to be a promising infrared (IR) NLO material, encompassing a strong SHG response with good phase matchability, wide band gap, high laser damage threshold (LDT), and large birefringence of 0.14@2.09 μm (5.7× AGSe, 10× BZGO) which overcomes the drawback of the small birefringence of AGSe. This work demonstrates that a highly polarized [GeOTe₃] motif can be used as a new basic building block (BBB) for IR NLO materials, providing a new idea for the exploration of new functional oxytellurides.