Comparison of the Different Bandgap Cavities in a Metallic Four-Mode Plasmonic Structure

Abstract

A four-mode anticrossing bandgap structure has been used to localize its delocalized Bragg modes, resulting in four different types of cavities with high quality factors. In particular, the quality factor associated to the long-range plasmonic cavities, at angles below the total internal reflection angle, is significantly higher than that reported on Moire plasmonic structures. Experiments demonstrate the existence of these long-range plasmonic cavities based on uniform gratings in the strong coupling regime. Moreover, this structure provides unique opportunities for reaching simultaneously the critical coupling of the two modes of the anticrossing bandgap, with a wavelength bandgap width smaller than that of traditional surface plasmon metallic Bragg mirrors. This implies a lower scattering power of the metallic grating.