Defect Diamond‐Like d ¹⁰ Metal Indium Selenium With Strong Second‐Harmonic Generation and Enhanced Laser‐Induced Damage Threshold

ABSTRACT The exploration of nonlinear optical (NLO) materials that combine strong second‐harmonic generation (SHG), a broad infrared (IR) transmission range, and a high laser‐induced damage threshold (LIDT) is important for diverse applications but remains challenging. This study reports the d ¹⁰ metal indium selenium, ZnIn ₂ Se ₄ (ZISe), and CdIn ₂ Se ₄ (CISe), which adopt a defect diamond‐like structure and show promise as potential IR NLO materials. They exhibit strong SHG efficiency of 2.7 and 1.3 times that of AGS, respectively, and achieve phase‐matching attributable to the reinforced birefringence—a feature not observed in their parent materials ZnSe and CdSe. Moreover, both compounds possess good infrared transparency within the measured range of 2.5–25 µm and demonstrate enhanced LIDTs, reaching 4.1 and 2.9 times that of AGS, respectively. Theoretical calculations indicate that the presence of cation vacancy defects and the ordered alignment of tetrahedral units are the key factors contributing to the enhanced NLO performance. This work establishes defect diamond‐like chalcogenides as a fruitful platform for discovering IR NLO materials.