Dual-to-triple mode coupling in Fabry-Pérot cavity-Gap-surface lattice supported by nano-optical metasurfaces

Multimode strong coupling metasurface systems provide an excellent platform for investigating energy-transfer processes in strong coupling regime. However, the simultaneous strong coupling of Fabry-Pérot (FP) cavity mode, Gap mode, and surface lattice resonance (SLR) mode remains largely unexplored. In this work, we propose what we believe to be a novel strategy to realize strong coupling of FP-Gap-SLR mode by employing a metal-insulator-metal (MIM) metasurface configuration combined with a thin sliver film. By integrating dielectric and metallic components, our design exhibits a pronounced Rabi splitting of 450.3 meV in the calculated reflection spectra of the hybrid system. Furthermore, the system allows tunable coupling transitions from dual-mode to triple-mode regimes simply by adjusting the metal's structural parameters, without the need for additional materials. Compared with conventional two-mode coupling systems, this multimode hybrid platform not only enhances the degree of mode hybridization but also holds significant promise for advancing both fundamental studies and practical applications of strong light-matter interactions.