A2SnS5: A Structural Incommensurate Modulation Exhibiting Strong Second‐Harmonic Generation and a High Laser‐Induced Damage Threshold (A=Ba, Sr)

• Published in: Angewandte Chemie International Edition Vol. 59; no. 29; pp. 11861 - 11865
• Main Authors: Li, Rui‐An, Zhou, Zhengyang, Lian, Yu‐Kun, Jia, Fei, Jiang, Xingxing, Tang, Ming‐Cong, Wu, Li‐Ming, Sun, Junliang, Chen, Ling
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 13.07.2020
• Edition: International ed. in English
• Subjects: Barium; Charge density waves; incommensurate modulation; Laser damage; Modulation; nonlinear optics; Optical properties; Phase matching; Physical properties; polychalcogenides; Second harmonic generation; Silver gallium sulfide; Strontium; sulfides; Superconductivity; Thermal expansion; Yield point
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202004059

Structural modulations have been recently found to cause some unusual physical properties, such as superconductivity or charge density waves; however, thus‐induced nonlinear optical properties are rare. We report herein two unprecedented incommensurately modulated nonlinear optical sulfides exhibiting phase matching behavior, A2SnS5 (A=Ba, Sr), with the (3+1)D superspace groups P21212(00γ)00s or P21(α0γ)0, featuring different modulations of the [Sn2S7]∞ belts. Remarkably, Ba2SnS5 exhibits an excellent second harmonic generation (SHG) of 1.1 times that of the benchmark compound AgGaS2 at 1570 nm and a very large laser‐induced damage threshold (LIDT) of 8×AgGaS2. Theoretical studies revealed that the structural modulations increase the distortions of the Sn/S building units by about 44 or 25 % in A2SnS5 (A=Ba, Sr), respectively, and enhance significantly the SHG compared with α‐Ba2SnSe5 without modulation. Besides, despite the smaller Eg, the A2SnS5 samples exhibit higher LIDTs owing to their smaller thermal expansion anisotropies (Ba2SnS5 (1.51)<Sr2SnS5 (2.08)<AgGaS2 (2.97)). Two incommensurately modulated nonlinear optical sulfides, Ba2SnS5 and Sr2SnS5, exhibit phase matching behavior and large laser‐induced damage thresholds. The second harmonic generation of Ba2SnS5 at 1570 nm is 1.1‐fold stronger than that of AgGaS2 as it benefits from the positional and occupational modulations.