Plasmonics for nanoimaging and nanospectroscopy.

The science of surface plasmon polaritons, known as "plasmonics," is reviewed from the viewpoint of applied spectroscopy. In this discussion, noble metals are regarded as reservoirs of photons exhibiting the functions of photon confinement and field enhancement at metallic nanostructures. The functions of surface plasmons are described in detail with an historical overview, and the applications of plasmonics to a variety of industry and sciences are shown. The slow light effect of surface plasmons is also discussed for nanoimaging capability of the near-field optical microscopy and tip-enhanced Raman microscopy. The future issues of plasmonics are also shown, including metamaterials and the extension to the ultraviolet and terahertz regions.