The mechanical exfoliation of naturally occurring layered materials has emerged as an easy and effective method for achieving ultrathin van der Waals (vdW) heterostructures with well-defined lattice orientations of the constituent two-dimensional (2D) material layers. Cylindrite is one such naturally occurring vdW heterostructure, where the superlattice is composed of alternating stacks of SnS₂-like and PbS-like layers. Although the constituent 2D lattices are isotropic, inhomogeneous strain occurring from local atomic alignment for forcing the commensuration makes the cylindrite superlattice structurally anisotropic. Here, we demonstrate the highly anisotropic optical responses of cylindrite thin flakes induced by the anisotropic crystal structure, including angle-resolved polarized Raman scattering, linear dichroism, and polarization-dependent anisotropic third-harmonic generation. Our results provide a promising approach for identifying various natural vdW heterostructure-based 2D materials with tailored optical properties and can be harnessed for realizing anisotropic optical devices for on-chip photonic circuits and optical information processing.

自然发生的层状材料的机械剥离已成为实现超薄范德华 (vdW) 异质结构的一种简单有效的方法，其构成的二维 (2D) 材料层具有明确的晶格取向。圆柱晶就是这样一种自然发生的 vdW 异质结构，其中超晶格由交替堆叠的 SnS ₂样和 PbS 样层。尽管组成的 2D 晶格是各向同性的，但由局部原子排列产生的非均匀应变迫使相称，使得圆柱晶超晶格在结构上具有各向异性。在这里，我们展示了由各向异性晶体结构引起的圆柱晶薄片的高度各向异性光学响应，包括角分辨偏振拉曼散射、线性二色性和偏振相关的各向异性三次谐波产生。我们的结果为识别具有定制光学特性的各种基于自然 vdW 异质结构的 2D 材料提供了一种很有前景的方法，并可用于实现片上光子电路和光信息处理的各向异性光学器件。