Breaking Through the Trade‐Off Between Wide Band Gap and Large SHG Coefficient in Mercury‐Based Chalcogenides for IR Nonlinear Optical Application
Mao‐Yin Ran, Shenghua Zhou, Wenbo Wei, Bing‐Xuan Li, Xintao Wu, Hua Lin, Qi‐Long Zhu
Abstract
Abstract It is substantially challenging for non‐centrosymmetric (NCS) Hg‐based chalcogenides for infrared nonlinear optical (IR‐NLO) applications to realize wide band gap ( E g > 3.0 eV) and sufficient phase‐matching (PM) second‐harmonic‐generation intensity ( d eff > 1.0 × benchmark AgGaS 2 ) simultaneously due to the inherent incompatibility. To address this issue, this work presents a diagonal synergetic substitution strategy for creating two new NCS quaternary Hg‐based chalcogenides, AEHgGeS 4 (AE = Sr and Ba), based on the centrosymmetric (CS) AEIn 2 S 4 . The derived AEHgGeS 4 displays excellent NLO properties such as a wide E g (≈3.04–3.07 eV), large PM d eff (≈2.2–3.0 × AgGaS 2 ), ultra‐high laser‐induced damage threshold (≈14.8–15 × AgGaS 2 ), and suitable Δ n (≈0.19–0.24@2050 nm), making them highly promising candidates for IR‐NLO applications. Importantly, such excellent second‐order NLO properties are primarily attributed to the synergistic combination of tetrahedral [HgS 4 ] and [GeS 4 ] functional primitives, as supported by detailed theoretical calculations. This study reports the first two NCS Hg‐based materials with well‐balanced comprehensive properties (i.e., E g > 3.0 eV and d eff > 1.0 × benchmark AgGaS 2 ) and puts forward a new design avenue for the construction of more efficient IR‐NLO candidates.