Plasmonics is a field of study that explores the interaction of light waves and metallic surfaces, and the resulting density waves of electrons that can be generated from this interaction. The resulting electron density wave that propagates along the surface of the metal is referred to as a surface plasmon polariton, or a surface plasmon. Owing to the strong frequency dependence of the complex permittivity of the metal, plasmons themselves exhibit strong variations with frequency, and this frequency dependence results in surface plasmon resonances. FDTD, DGTD and MODE are ideally suited to studying plasmonic devices.