Lifetime of nano-plasmonic states

Molding the flow of light at the sub-wavelength scale has always been one of the greatest challenges of photonics, as it would allow the realization of optical circuits with a degree of integration similar to that achieved in integrated electronics. Strongly localized eigenstates of an electromagnetic (EM) field exist in small clusters of regular metallic inclusions embedded in an otherwise uniform dielectric host. The electromagnetic field can be restricted to have large amplitude in spatial regions whose linear size is much smaller than the wavelength. This ultra-localization of an EM field is achieved with the help of surface plasmons in the metallic inclusions. These plasmons screen the EM field, essentially cancelling it outside the volume of the eigenstate. This phenomenon has been proposed as the basis for a SPASER device, namely, Surface Plasmon Amplification by Stimulated Emission of Radiation [1]. This SPASER would be a source of strong, coherent EM radiation with a size that can be much smaller than the wavelength. In this report we present results for such states which go beyond the quasistatic approximation. That is necessary in order to analyze the radiative and dissipative properties of those states, e.g., the radiative and dissipative losses.