Fig. 7: Single-particle spasers.
a A schematic of a single-particle spaser design involving a gold core covered by a silica shell doped with an organic dye (Oregon Green 488)36. b Scanning electron microscope image of spaser nanoparticles36. c Radiation from a metal-semishell-capped spaser. The silver semishell generates feedback with localized surface plasmons, whereas the porous silica core provides optical gain138. d A polar plot of the power flow from the spaser featured in c at different angles of incidence138. e A spaser design consisting of a gold nanorod covered with an organic dye-gain material embedded in a mesoporous silica shell139. f The spontaneous emission (SE) and amplified spontaneous emission (ASE) from the spaser system in e with different dye concentrations. Each spectrum is normalized to the peak of the spaser emission139. g A schematic of a core-shell spaser with a gold core covered by a three-level dye system embedded in a silica shell140. h The evolution of the full width at half maximum (FWHM) (blue) and emission intensity (red) of the spaser in g vs. the pump energy140.
