Understanding the plane wave excitation of the metal-insulator-metal gap plasmon mode of a nanoribbons periodic array: role of insulator-metal-insulator lattice mode

Abstract

A simple semi-analytical single mode model describing the mechanism of metal-insulator-metal gap plasmon mode excitation by a plane wave is proposed. The role of the insulator-metal-insulator (IMI) lattice mode is highlighted. Although many other works addressed this issue, the crucial role of this mode has never been demonstrated before. This mode appears as the missing link that ensures energy transfer between the incident plane wave and the metal-insulator-metal (MIM) gap plasmon mode. In this single mode model, the grating layer, the host layer of the IMI lattice mode, is viewed as an effective homogeneous medium, and the scattering matrix characterizing the interaction between the IMI lattice mode and the MIM gap plasmon mode is easily computed. The proposed simplified model allows us to grasp the physical origin of the modes of the system and to predict accurately the resonance frequencies of the 1D structure. These modes are classified in symmetric and antisymmetric modes. The incident field, by its symmetry properties, acts on the system as a selection rule, activating a class of modes with the same symmetry properties as itself.