Wang Han, Chen Quan, Cao Yi, Sang Weihui, Tan Feixia, Li Honghong, Wang Tinghao, Gan Yang, Xiang Du, Liu Tao
Shanghai Frontiers Science Research Base of Intelligent Optoelectronics and Perception, Institute of Optoelectronics, and Department of Materials Science, Fudan University, Shanghai 200433, China.
State Key Laboratory of Integrated Chips and Systems, Frontier Institute of Chip and System, Fudan University, Shanghai 200433, China.
Nano Lett. 2024 Mar 20;24(11):3413-3420. doi: 10.1021/acs.nanolett.4c00039. Epub 2024 Mar 8.
Two-dimensional (2D) NbOI demonstrates significant second-harmonic generation (SHG) with a high conversion efficiency. To unlock its full potential in practical applications, it is desirable to modulate the SHG behavior while utilizing the intrinsic lattice anisotropy. Here, we demonstrate direction-specific modulation of the SHG response in NbOI by applying anisotropic strain with respect to the intrinsic lattice orientations, where more than 2-fold enhancement in the SHG intensity is achieved under strain along the polar axis. The strain-driven SHG evolution is attributed to the strengthened built-in piezoelectric field (polar axis) and the enlarged Peierls distortions (nonpolar axis). Moreover, we provide quantifications of the correlation between strain and SHG intensity in terms of the susceptibility tensor. Our results demonstrate the effective coupling of orientation-specific strain to the anisotropic SHG response through the intrinsic polar order in 2D nonlinear optical crystals, opening a new paradigm toward the development of functional devices.
二维（2D）铌氧碘化物表现出显著的二次谐波产生（SHG），且转换效率很高。为了在实际应用中充分发挥其潜力，在利用其固有晶格各向异性的同时调节SHG行为是很有必要的。在此，我们通过相对于固有晶格取向施加各向异性应变，证明了铌氧碘化物中SHG响应的方向特异性调制，其中沿极轴方向施加应变时，SHG强度实现了超过两倍的增强。应变驱动的SHG演化归因于增强的内建压电场（极轴）和扩大的派尔斯畸变（非极轴）。此外，我们根据极化率张量对应变与SHG强度之间的相关性进行了量化。我们的结果表明，通过二维非线性光学晶体中的固有极性有序，特定取向应变与各向异性SHG响应实现了有效耦合，为功能器件的开发开辟了新的范例。
