LiVTeO5: a mid-infrared nonlinear optical vanadium tellurate crystal exhibiting enhanced second harmonic generation activities and notable birefringence

Abstract

Mid-infrared (IR) nonlinear optical (NLO) crystals are of great interest for applications in laser science and technology. Nevertheless, the pursuit of mid-IR NLO crystals displaying exceptional comprehensive performance remains a challenge. Herein, an effective strategy is achieved by combining two distinct species of second-order Jahn–Teller distorted cations, Te⁴⁺ and V⁵⁺, into one compound. A prospective NLO vanadium tellurate crystal, LiVTeO₅, was synthesized via spontaneous crystallization, which crystallizes in the orthorhombic space group P2₁2₁2₁ (no. 19) with a three-dimensional framework structure. The optical measurements revealed that LiVTeO₅ manifests a large band gap of 3.2 eV and an intense second-harmonic-generation (SHG) activity of 3.2 × KDP. Moreover, it displays an extensive transmittance region beyond 5.0 μm, along with a discernible birefringence of 0.091, thereby facilitating the realization of the phase matching conditions. Additionally, structural analysis combined with first-principles calculations elucidate that the [TeO₃] and [VO₅] active building blocks primarily contribute to the intriguing macroscopic nonlinearity and notable birefringence observed in LiVTeO₅. These findings highlight the optimized overall properties of LiVTeO₅, which makes it a potential mid-IR NLO material.