Kim Wontaek, Jeong Gyouil, Oh Juseung, Kim Jihun, Watanabe Kenji, Taniguchi Takashi, Ryu Sunmin
Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 37673, Korea.
Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
ACS Nano. 2023 Oct 24;17(20):20580-20588. doi: 10.1021/acsnano.3c07428. Epub 2023 Oct 6.
The efficient optical second-harmonic generation (SHG) of two-dimensional (2D) crystals, coupled with their atomic thickness, which circumvents the phase-match problem, has garnered considerable attention. While various 2D heterostructures have shown promising applications in photodetectors, switching electronics, and photovoltaics, the modulation of nonlinear optical properties in such heterosystems remains unexplored. In this study, we investigate exciton-sensitized SHG in heterobilayers of transition metal dichalcogenides (TMDs), where photoexcitation of one donor layer enhances the SHG response of the other as an acceptor. We utilize polarization-resolved interferometry to detect the SHG intensity and phase of each individual layer, revealing the energetic match between the excitonic resonances of donors and the SHG enhancement of acceptors for four TMD combinations. Our results also uncover the dynamic nature of interlayer coupling, as made evident by the dependence of sensitization on interlayer gap spacing and the average power of the fundamental beam. This work provides insights into how the interlayer coupling of two different layers can modify nonlinear optical phenomena in 2D heterostructures.
二维（2D）晶体的高效光学二次谐波产生（SHG），连同其原子厚度，规避了相位匹配问题，已引起了相当大的关注。虽然各种二维异质结构在光电探测器、开关电子学和光伏领域已显示出有前景的应用，但此类异质系统中非线性光学性质的调制仍未得到探索。在本研究中，我们研究了过渡金属二硫属化物（TMD）异质双层中的激子敏化SHG，其中一个供体层的光激发增强了另一个作为受体层的SHG响应。我们利用偏振分辨干涉测量法来检测每个单独层的SHG强度和相位，揭示了四种TMD组合中供体的激子共振与受体的SHG增强之间的能量匹配。我们的结果还揭示了层间耦合的动态性质，这通过敏化对层间间隙间距和基波光束平均功率的依赖性得以体现。这项工作为两个不同层的层间耦合如何改变二维异质结构中的非线性光学现象提供了见解。
