Figure 13.

(A) Schematic image of the strong coupling between the plasmon and molecular resonances. Here, |g⟩ and |e⟩ are the ground and excited states of the two-level system, respectively; |0⟩ and |1⟩ are the zero- and one-photon states of the plasmon resonance; 2ℏg indicates vacuum Rabi splitting (VRS), which is the energy split of the excited state of the strong coupling system formed by the two-level system and plasmonic resonance. The red and blue arrows indicate the two coupled resonance energies. (B) Calculated anticrossing property of the strong coupling between a plasmon and an exciton of a two-level system with a coupling energy of 400 meV. Inset: Absorption spectrum of the aqueous solution of R6G (green curve). Reproduced with permission from ref (17). Copyright 2021 Royal Society of Chemistry.