A<sub>2</sub>SnS<sub>5</sub>: A Structural Incommensurate Modulation Exhibiting Strong Second‐Harmonic Generation and a High Laser‐Induced Damage Threshold (A=Ba, Sr)
Rui‐An Li, Zhengyang Zhou, Yu‐Kun Lian, Fei Jia, Xingxing Jiang, Mingcong Tang, Li‐Ming Wu, Junliang Sun, Ling Chen
Abstract
Abstract 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, A 2 SnS 5 (A=Ba, Sr), with the (3+1)D superspace groups P 2 1 2 1 2(00 γ )00 s or P 2 1 ( α 0 γ )0, featuring different modulations of the [Sn 2 S 7 ] ∞ belts. Remarkably, Ba 2 SnS 5 exhibits an excellent second harmonic generation (SHG) of 1.1 times that of the benchmark compound AgGaS 2 at 1570 nm and a very large laser‐induced damage threshold (LIDT) of 8×AgGaS 2 . Theoretical studies revealed that the structural modulations increase the distortions of the Sn/S building units by about 44 or 25 % in A 2 SnS 5 (A=Ba, Sr), respectively, and enhance significantly the SHG compared with α‐Ba 2 SnSe 5 without modulation. Besides, despite the smaller E g , the A 2 SnS 5 samples exhibit higher LIDTs owing to their smaller thermal expansion anisotropies (Ba 2 SnS 5 (1.51)<Sr 2 SnS 5 (2.08)<AgGaS 2 (2.97)).