ABSTRACT
This chapter discusses localized polaritons of basic nanostructures used in the areas of photonics and plasmonics. It reviews localized polaritons of the basic single-particle systems of the planar, cylindrical, and spherical geometries. The chapter shows that regardless of structures' material and geometrical parameters, all localized polaritons can be classified as the transmission, radiation, and absorption eigenmodes featuring different distributions of the external eigenfields. These polaritons are inherent to both photonic and plasmonic structures but possess slightly different eigenfields. In general, localized polaritons are virtual; they cannot appear as the excited fields and should be considered as resonant response characteristics only. However, under certain conditions that require a particular matching of the material and geometrical parameters, localized polaritons can become true eigenmodes with fully physical fields that enable pronounced energy transfer in a system.
