Tuning of surface plasmons in visible and near infrared range using plasmonic crystals

Surface plasmons (SPs) are electromagnetic waves propagating along metallic-dielectric interfaces which can be supported by structures at broad scales and can find extensive applications from sensing to optical waveguiding. SPs can take different forms, from free waves to localized oscillations depending on different geometries. The excitation of the spectrum of a plasmonic nanostructure is determined by its collective electronic oscillations. Furthermore, the plasmon modes of a nanostructure are determined by its composition, scale and shape. Plasmonic coaxial nanostructures have drawn considerable attention recently because of their fascinating properties and their great potential as an important canditate of ultracompact optical devices. Here, we demonstrate tunable optical response using coaxial apertures with ultrasmall gaps (less than 50 nm) and nanorods with square lattice fabricated using focused ion beam milling and e-beam lithography followed by argon ion milling, respectively.