Cd2Nb2Te4O15: A Novel Pseudo‐Aurivillius‐Type Tellurite with Unprecedented Nonlinear Optical Properties and Excellent Stability

Abstract

AbstractOxides are emerging candidates for mid‐infrared (mid‐IR) nonlinear optical (NLO) materials. However, their intrinsically weak second harmonic generation (SHG) effects hinder their further development. A major design challenge is to increase the nonlinear coefficient while maintaining the broad mid‐IR transmission and high laser‐induced damage threshold (LIDT) of the oxides. In this study, it is reported on a polar NLO tellurite, Cd2Nb2Te4O15 (CNTO), featuring a pseudo‐Aurivillius‐type perovskite layered structure composed of three types of NLO active groups, including CdO6 octahedra, NbO6 octahedra, and TeO4 seesaws. The uniform orientation of the distorted units induces a giant SHG response that is ≈31 times larger than that of KH2PO4, the largest value among all reported metal tellurites. Additionally, CNTO exhibits a large band gap (3.75 eV), a wide optical transparency window (0.33–14.5 µm), superior birefringence (0.12@ 546 nm), high LIDT (23 × AgGaS2), and strong acid and alkali resistance, indicating its potential as a promising mid‐IR NLO material.