Cs4Zn5P6S18I2: the Largest Birefringence in Chalcohalide Achieved by Highly Polarizable Nonlinear Optical Functional Motifs

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 19; no. 46
• Main Authors: Xian‐Dan Chai, Ming‐Ze Li, Shu‐Juan Lin, Wen‐Fa Chen, Xiao‐Ming Jiang, Bin‐Wen Liu, Guo‐Cong Guo
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.11.2023
• Subjects: Anisotropy; Birefringence; Electronegativity; Electropositivity; Energy gap; Ethanol; Harmonic generations; Laser damage; Nanotechnology; Nonlinear optics; Phase matching; Silver gallium sulfide; Yield point
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202303847

Chalcohalides not only keep the balance between the nonlinear optical (NLO) coefficient and wide band gap, but also provide a promising solution to achieve sufficient birefringence for phase‐matching ability in NLO crystals. In this study, a novel chalcohalide, Cs4Zn5P6S18I2 (1) is successfully synthesized, by incorporating the highly electropositive Cs and the large electronegative I element into the zinc thiophosphate. Its 3D open framework features an edge‐shared by distorted [ZnS4], ethanol‐like [P2S6], and unusual [ZnS2I2] polyhedrons, which is inconsistent with the soft‐hard‐acids‐bases theory. Remarkably, compound 1 simultaneously exhibits the large second‐harmonic generation (SHG, 1.1×AgGaS2, @1.3 µm) and a wide band gap (3.75 eV) toward a high laser‐induced damage threshold (16.7×AgGaS2, @1.06 µm), satisfying the rigorous requirements for a prominent infrared NLO material with concurrent SHG intensity (≥0.5×AGS) and band gap (≥3.5 eV). Moreover, to the best of the knowledge, the experimental result shows that phase 1 has the largest birefringence (0.108, @546 nm) in chalcohalide and meets phase‐matching behavior demand originating from the polarizable anisotropy of NLO‐functional motifs. This finding may provide great opportunities for designing birefringent chalcohalides.