Magnetic plasmon induced ultra-narrow perfect light absorption at visible frequency for gas sensing

Abstract

We theoretically demonstrate an ultranarrow perfect light absorption (PIA) of a 3D metamaterial due to the strong coupling between the magnetic plasmon of the Au vertical split-ring resonator (VSRR) and the surface plasmon polariton propagating above the Au film. Through lifting the VSRRs above the metallic film to decrease the dielectric substrate effect, the linewidth of 1.9 nm of the PIA is obtained. Our proposed 3D metamaterial shows the high sensitivity (S = 711 nm/RIU, S* = 13/RIU) and figure of merit (FoM =374, FoM* =1.3×105), which could be used for optical gas sensing in visible frequency range.