He Chuan, Wu Ruowei, Zhu Lipeng, Huang Yuanyuan, Du Wanyi, Qi Mei, Zhou Yixuan, Zhao Qiyi, Xu Xinlong
Shaanxi Joint Lab of Graphene, International Collaborative Center on Photoelectric Technology and Nano Functional Materials, State Key Laboratory of Photon-Technology in Western China Energy, Institute of Photonics & Photon-Technology, Northwest University, Xi'an 710069, China.
School of Electronic Engineering, Xi'an University of Posts & Telecommunications, Xi'an 710121, China.
J Phys Chem Lett. 2022 Jan 13;13(1):352-361. doi: 10.1021/acs.jpclett.1c03571. Epub 2022 Jan 5.
Strain engineering is an attractive method to induce and control anisotropy for polarized optoelectronic applications with two-dimensional (2D) materials. Herein, we have investigated the nonlinear optical coefficient dispersion relationship and the second-harmonic generation (SHG) pattern evolution under the uniaxial strains for graphene, WS, GaSe, and InSe monolayers. The uniaxial strain can break the in-plane symmetry of 2D materials, leading to both trade-off breaking of the nonlinear coefficient and new emergent nonlinear coefficients. In such a case, a classical sixfold ϕ-dependent SHG pattern is transformed into a distorted sixfold SHG pattern under the strain. Due to the lattice symmetry breaking and the uneven charge density distribution in strained 2D materials, the SHG patterns also depend on the excitation photon energy. The results could give a guide for the SHG pattern analysis in experiments, suggesting strain engineering on 2D materials for the tunable anisotropy in polarized and flexible nonlinear optical devices.
应变工程是一种用于二维（2D）材料的极化光电器件中诱导和控制各向异性的有吸引力的方法。在此，我们研究了石墨烯、WS、GaSe和InSe单层在单轴应变下的非线性光学系数色散关系和二次谐波产生（SHG）图案演变。单轴应变会破坏二维材料的面内对称性，导致非线性系数的权衡打破以及新出现的非线性系数。在这种情况下，经典的六重ϕ相关SHG图案在应变下转变为扭曲的六重SHG图案。由于应变二维材料中的晶格对称性破坏和电荷密度分布不均匀，SHG图案还取决于激发光子能量。这些结果可为实验中的SHG图案分析提供指导，表明在二维材料上进行应变工程以实现极化和柔性非线性光学器件中的可调各向异性。
