Ultrafast Investigation of the Strong Coupling System between Square Ag Nanohole Array and Monolayer WS₂

Recent advancements in the study of light-matter interactions between optical cavities and two-dimensional materials have underscored the significance of strong coupling phenomena, facilitating innovative developments in optical devices and quantum information processing. In this study, we explored the interaction between Bloch-surface plasmon polaritons from a square Ag nanohole array and A exciton of monolayer WS₂, demonstrating a significant Rabi splitting of 74 meV via angle-resolved transient absorption spectroscopy. By analyzing the damping process of the upper and lower branches, we observe that the lower branch decays significantly faster than the upper branch. These findings not only enhance our understanding of exciton-polariton but also point to potential applications in Bose-Einstein condensation, nanophotonics, and quantum information.