Tellurate polymorphs with high-performance nonlinear optical switch property and wide mid-IR transparency

Abstract

Here, we report two tellurate polymorphs, α- and β-Li₂HfTeO₆, undergoing a fast thermally induced phase transition that originates from the symmetry breaking of HfO₆ and TeO₆ octahedra, thus behaving as potential nonlinear optical (NLO) switches. It was found that Li₂HfTeO₆ possesses a relatively low transition temperature at around 144 °C and good switching reversibility with a remarkable NLO switching contrast (∼13.5), which makes it an excellent candidate for NLO switches. In addition, the two polymorphs show wide infrared (IR) absorption edges (∼8 μm) with a high laser-induced damage threshold (>1 GW cm⁻³), which is suitable for mid-IR NLO application. Further, theoretical analysis reveals that both HfO₆ and TeO₆ octahedra are NLO-active units and the atomic displacements in these units contribute greatly to NLO switching.