Tripathi Ravi P N, Gao Jie, Yang Xiaodong
Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, MO, 65409, USA.
Sci Rep. 2021 Apr 19;11(1):8510. doi: 10.1038/s41598-021-88143-5.
Vertically stacked van der Waals (vdW) heterostructures have introduced a unique way to engineer optical and electronic responses in multifunctional photonic and quantum devices. However, the technical challenges associated with the artificially fabricated vertical heterostructures have emerged as a bottleneck to restrict their proficient utilization, which emphasizes the necessity of exploring naturally occurring vdW heterostructures. As one type of naturally occurring vdW heterostructures, franckeite has recently attracted significant interest in optoelectronic applications, but the understanding of light-matter interactions in such layered mineral is still very limited especially in the nonlinear optical regime. Herein, the anisotropic Raman scattering and third-harmonic generation (THG) from mechanically exfoliated franckeite thin flakes are investigated. The observed highly anisotropic Raman modes and THG emission patterns originate from the low-symmetry crystal structure of franckeite induced by the lattice incommensurability between two constituent stacked layers. The thickness-dependent anisotropic THG response is further analyzed to retrieve the third-order nonlinear susceptibility for franckeite crystal. The results discussed herein not only provide new insights in engineering the nonlinear light-matter interactions in natural vdW heterostructures, but also develop a testbed for designing future miniaturized quantum photonics devices and circuits based on such heterostructures.
垂直堆叠的范德华（vdW）异质结构为多功能光子和量子器件中的光学和电子响应工程引入了一种独特的方法。然而，与人工制造的垂直异质结构相关的技术挑战已成为限制其有效利用的瓶颈，这凸显了探索天然存在的vdW异质结构的必要性。作为一种天然存在的vdW异质结构，黄铅矿最近在光电子应用中引起了极大的兴趣，但对这种层状矿物中光与物质相互作用的理解仍然非常有限，尤其是在非线性光学领域。在此，对机械剥离的黄铅矿薄片的各向异性拉曼散射和三次谐波产生（THG）进行了研究。观察到的高度各向异性拉曼模式和THG发射图案源于黄铅矿的低对称晶体结构，该结构由两个组成堆叠层之间的晶格失配引起。进一步分析了厚度依赖的各向异性THG响应，以获取黄铅矿晶体的三阶非线性极化率。本文讨论的结果不仅为天然vdW异质结构中的非线性光与物质相互作用工程提供了新的见解，还为基于此类异质结构设计未来的小型化量子光子器件和电路开发了一个试验平台。
