Ultra-strong surface plasmon amplification characteristic of a spaser based on gold–silver core–shell nanorods

We proposed an efficient spaser based on gold–silver core–shell nanorods (NRs) encapsulated by an outer silica shell doped with a gain medium. The optical characteristics of the spaser were numerically simulated based on the finite element method (FEM). The results showed that the localized surface plasmon resonance (LSPR) amplification characteristics of the spaser strongly depend on the thickness of silver shell, the aspect ratio of the inner gold NRs, and the polarization direction of the incident light. And, the maximum absolute value of optical cross-section of the spaser can reach 21,824 μm2, which is about 1115, 523, and 18 times higher than that of spasers based on the gold NRs, the silver NRs, and the silver–gold core–shell NRs, respectively. The ultra-strong surface plasmon amplification characteristics of the spaser have potential applications in optical information storage, high sensitivity biochemical sensing, and medical engineering.