Plasmon excitation and induced emission with a plasmonic self-organized crystal

In this paper, we describe the plasmonic and plasmon-photon coupling properties of nanostructured metallic films obtained by a self-assembly protocol. A gold layer is deposited on top of a self-assembled deposition of silica beads (artificial opal), which thus acts as a template. Atomic-force and scanning-electron microscopies demonstrates a periodic pattern on the metal surface with groove depth (here labelled h) ranging from 55 to 150 nm. By optical gonioreflectometry, the surface plasmon modes of this structure are probed: plasmon creation appears as an absorption dip in the reflection spectra. The plasmon dispersion relation is probed as a function of h and shows, for the smaller values of h, a good agreement with an analytical model for vanishing h. By depositing nanocrystals on the structure and measuring the fluorescence radiation pattern, we demonstrate a method to estimate the plasmon extraction (plasmon-to-photon coupling) efficiency. Finally, we use photoemission electron microscopy to map the electric field of the plasmonic modes and characterize both propagative surface plasmon and localized (“hot spot”) plasmon modes.