Light–matter interactions between plasmonic and excitonic modes have attracted considerable interest in recent years. A major challenge in achieving strong coupling is the identification of suitable metallic nanostructures that combine tight field confinement with sufficiently low losses. Here, we report on a room-temperature study on the interaction of tungsten disulfide (WS2) monolayer excitons with a hybrid plasmon polariton (HPP) mode supported by nanogroove grating structures milled into single-crystalline silver flakes. By engineering the depth of the nanogroove grating, we can change the character of the HPP mode from propagating surface plasmon polariton-like (SPP-like) to localized surface plasmon resonance-like (LSPR-like). Using reflection spectroscopy, we demonstrate strong coupling with a Rabi splitting of 68 meV between the WS2 monolayer excitons and the lower HPP branch for an optimized nanograting configuration with 60 nm deep nanogrooves. In contrast, only weak coupling between the constituents is observed for shallower and deeper nanogratings since either the field confinement provided by the HPP is not sufficient or the damping is too large. The possibility to balance the field confinement and losses render nanogroove grating structures an attractive platform for future applications.

中文翻译：

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室温下 WS2 单层激子与混合等离子体激元之间的强耦合

近年来，等离子体和激子模式之间的光与物质相互作用引起了人们极大的兴趣。实现强耦合的一个主要挑战是识别合适的金属纳米结构，将紧密的场限制与足够低的损耗结合起来。在这里，我们报告了二硫化钨（WS）相互作用的室温研究2）具有混合等离子体激元（HPP）模式的单层激子，由研磨成单晶银片的纳米槽光栅结构支持。通过设计纳米凹槽光栅的深度，我们可以将 HPP 模式的特征从类传播表面等离子体激元（类 SPP）改变为类局域表面等离子体共振（类 LSPR）。使用反射光谱，我们证明了 WS 之间具有 68 meV 拉比分裂的强耦合2单层激子和较低的 HPP 分支可实现具有 60 nm 深纳米凹槽的优化纳米光栅配置。相比之下，对于较浅和较深的纳米光栅，仅观察到成分之间的弱耦合，因为 HPP 提供的场限制不足或阻尼太大。平衡场限制和损耗的可能性使纳米凹槽光栅结构成为未来应用的有吸引力的平台。