Boosting multi-mode strong coupling in a hybrid vertical split-ring resonator metamaterial for magnetoplasmonic sensing

Achieving multi-mode strong coupling between different modes in nanoscale is challenging due to the large damping rate of the system. Here, we report an effective way to achieve multi-mode plasmonic and magnetic resonances strong coupling via introducing the localized surface plasmon resonance into the designed dimer vertical split-ring resonator (DVSRR) magnetoplasmonic metamaterial. Due to strong near-field enhancement and far-field scattering suppression, the Rabi splitting energy could be enhanced from 144 meV to 286 meV. Benefiting from the multi-mode strong coupling, three distinct Kerr reversals are obtained in the Kerr spectrum, which provides a feasible route for achieving multi-mode magnetoplasmon-sensor, with high FoM of 4265/RIU, 135/RIU and 3995/RIU, respectively. The hybrid branches are analyzed with weighting coefficients that are calculated by the three coupled oscillator model.