Surface plasmon amplification characteristics of an active three-layer nanoshell-based spaser

Surface plasmon (SP) amplification by stimulated emission of radiation (spaser) of the active nanoshell with three-layer silica-gold-silica structure is proposed. The properties of the spaser are numerically analyzed based on Mie theory. The results show that the nanoshell-based spaser is one order of magnitude higher than the nanosphere-based and nanoegg-based spasers in the surface plasmon amplification, but the gain threshold kthre of the silica is nearly one order of magnitude lower. In addition, the behavior of the nanoshell-based spaser depends on structural parameters that are explained by the quenching effect, plasmon hybridization theory, and dynamic photon-plasmon coupling mechanism. By optimizing the structure parameters of the layered nanoshell, an extremely high spaser enhancement over a wider operating range of wavelength tunings was obtained, both aspects having important significance in practical applications.