Evidence of the retardation effect on the plasmonic resonances of aluminum nanodisks in the symmetric/asymmetric environment

A single metallic nanodisk is the simplest plasmonic nanostructure, but it robust enough to generate a Fano resonance in forward and backward scattering spectra by increment of height symmetric asymmetric dielectric environment. Thanks phase retardation effect, non-uniform distribution electric field along aluminum (Al) generates out-of-plane higher-order modes, which interfere with dipolar mode subsequently result Fano-lineshape spectra. Meanwhile, symmetry-breaking effect substrate refractive index environment further accelerate contribute appearance modes. The experimental results on periodic Al arrays different heights confirm retardation-induced higher modes blueshifted main dips transmission prove dominant role resonances taller nanodisk.