Tunable dual-band plasmonic perfect absorber and its sensing applications

We theoretically present a tunable dual-band perfect absorber in the visible and near-infrared regions for sensing applications. The absorber consists of a periodic metal-dielectric-metal shell-core nanorod array and a thick metal film separated by a periodic dielectric nanorod array. Two narrow perfect absorption bands (98.2% and 99.7%) are achieved due to the synergy of localized surface plasmons (LSPs), propagating surface plasmons (PSPs) and lattice resonances. The two narrow bands both are sensitive to the refractive index change and the maximum sensitivity is 783.705 nm/RIU (RIU is the refractive index unit). These enable the structure to have great potential in the fields of perfect absorbers, plasmonic sensors, and filters.