Surface plasmon polariton

Summary

A surface plasmon polariton is an electromagnetic wave that travels along the interface between a metal and a dielectric and decays exponentially on both sides. It is a coupled oscillation of the light field and of the free electrons at the metal surface. It exists only when the real part of the metal permittivity is negative and larger in size than the dielectric permittivity. Its wavelength is shorter than that of light of the same frequency, which lets it concentrate light below the diffraction limit.