  We present a semi-analytical model of the resonance phenomena occurring in a
hybrid system made of a 1D array of periodic subwavelength slits deposited on
an insulator/graphene layer. We show that the spectral response of this hybrid
system can be fully explained by a simple semi-analytical model based on a weak
and strong couplings between two elementary sub-systems. The first elementary
sub-system consists of a 1D array of periodic subwavelength slits viewed as a
homogeneous medium. In this medium lives a metal-insulator-metal lattice mode
interacting with surface and cavity plasmon modes. A weak coupling with surface
plasmon modes on both faces of the perforated metal film leads to a broadband
spectrum while a strong coupling between this first sub-system and a second one
made of a graphene-insulator-metal gap leads to a narrow band spectrum. We
provide a semi-analytical model based on these two interactions allowing to
efficiently access the full spectrum of the hybrid system.
