Spaser based on Fano resonance in a rod and concentric square ring-disk nanostructure

Abstract

This paper reports a spaser based on Fano resonance of a plasmonic nanostructure consisting of a rod and concentric square ring-disk structure coated with a layer of gain media. The amplification of the dark quadrupolar mode at the Fano resonance wavelength causes the spaser with a high Purcell factor of 3.24 × 107, a high signal to noise ratio of 4.4 × 106, and a lower threshold of 0.02086. These significant optical properties are attributed to the greatly enhanced spontaneous emission and depressed radiation loss supported by the strong localized dark mode at the Fano resonance wavelength.