Interaction among plasmonic resonances in a gold film embedding a two-dimensional array of polymeric nanopillars

Nanostructured surfaces have proven to be effective in controlling the electric field distribution and triggering
a series of interesting physical effects. In particular, ordered metallic lattices with a typical size of the same
order of magnitude of the wavelength of the incident radiation exhibit extraordinary transmission and reflection
properties and represent a sensitive tool to exploit surface plasmon resonance for sensing applications. We
investigated, either by experimental structural and optical measurements or by modeling and calculations, samples
consisting of a two-dimensional array of polymeric pillars embedded in a gold film. In particular, we analyzed
the dependence of the plasmonic resonance on the pillar size. We showed that a peculiar interplay among
localized modes and propagating surface plasmon polaritons exists for some selected conditions and affects
the spectral distribution, lifetime, and field configuration of the plasmonic excitations.