Ab initio analysis of hybridization models for two near-field coupled “bright” and “dark” meta-atoms

Coupled sub-wavelength resonators based on metals used in microwave range or for plasmonic resonances must be carefully engineered to produce sharp spectral features, using most notably Dark Modes and Fano resonances. The simple and popular version of coupled-oscillator phenomenology, in spite of its intuitive appeal, is eventually misleading as it merges near-field coupling to radiative effects that also contribute to coupling. Its connection with outer field is also awkward for the conception of simple or double plasmonic metasurfaces, which require more physical descriptions to be properly handled. The comparison with the more complete time-Coupled-Mode-Theory is tackled in this respect. It shows that even in the limit case of large near-field coupling dominance, unphysical trends are appearing much more strongly in one model than in the other. We also underline the less-known point that such dominant near-field coupling is similar to the Förster energy transfer very common in molecular photonics.