Optical beam shifts, such as the Goos–Hänchen (GH) shift and the Imbert–Fedorov (IF) shift, are fundamental optical phenomena. However, because these shifts are so minute, direct measurement is challenging, and obtaining an optical shift spectrum is even more difficult. Here, we successfully obtained GH and IF shift spectra using a beam displacement amplification technique. The optical shift spectrum of graphene shows very good agreement with the predicted results. Meanwhile, we observed two distinct peaks in the optical shift spectrum of {{\rm WS}_2}${{\rm WS}_2}$, corresponding to the A- and B-exciton transitions at the {K}${K}$-point in the Brillouin zone. More importantly, when graphene is stacked on {{\rm WS}_2}${{\rm WS}_2}$ to form a van der Waals heterostructure, the A-exciton characteristic of {{\rm WS}_2}${{\rm WS}_2}$ increases by an order of magnitude, which is essentially different from absorption and fluorescence spectra. Furthermore, refractive index change can be precisely captured by GH shift spectroscopy, which proves the optical shift spectrum to be an ideal candidate for a highly sensitive biosensor. Optical shift spectroscopy could enable new applications for nanophotonic devices and provide a platform for the study of intrinsic properties of two-dimensional materials, especially for van der Waals heterostructure.

中文翻译：

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二维材料中的光移光谱

光束位移，例如古斯-汉兴 (GH) 位移和安伯特-费多罗夫 (IF) 位移，是基本的光学现象。然而，由于这些位移非常微小，直接测量具有挑战性，并且获得光学位移光谱更加困难。在这里，我们使用光束位移放大技术成功获得了 GH 和 IF 位移光谱。石墨烯的光学位移光谱与预测结果非常吻合。同时，我们在{{\rm WS}_2}${{\rm WS}_2}$的光移谱中观察到两个不同的峰，对应于布里渊区{K}${K}$点处的 A 和 B 激子跃迁。更重要的是，当石墨烯堆叠在{{\rm WS}_2}${{\rm WS}_2}$上形成范德华异质结构时，{{\rm WS}_2}${{\rm WS}_2}$的A激子特性增加了一个数量级，这与吸收和荧光光谱。此外，GH位移光谱可以精确捕获折射率变化，这证明光学位移光谱是高灵敏度生物传感器的理想候选者。光位移光谱可以为纳米光子器件带来新的应用，并为研究二维材料的本征特性提供一个平台，特别是范德华异质结构。