Multiple resonance modes in an optical absorber are necessary for nanophotonic devices and encounter a challenge in the visible range. This article designs a multiple-channel plasmonic metamaterial absorber (PMA) that comprises a hexagonal arrangement of metal-shell nanorods in a unit cell over a continuous thin metal layer, operating in the visible range of the sensitive refractive index (RI) and temperature applications. Finite element method simulations are utilized to investigate the physical natures, such as the absorptance spectrum, magnetic flux and surface charge densities, electric field intensity, and electromagnetic power loss density. The advantage of the proposed PMA is that it can tune either three or five absorptance channels with a narrowband in the visible range. The recorded sensitivity and figure of merit (S, FOM) for modes 1-5 can be obtained (600.00 nm/RIU, 120.00), (600.00 nm/RIU, 120.00 RIU-1), (600.00 nm/RIU, 120.00 RIU-1), (400.00 nm/RIU, 50.00 RIU-1), and (350.00 nm/RIU, 25.00 RIU-1), respectively. Additionally, the temperature sensitivity can simultaneously reach 0.22 nm/°C for modes 1-3. The designed PMA can be suitable for RI and temperature sensing in the visible range.
Keywords: multiple resonance modes; plasmonic metamaterial absorber; temperature sensitivity; visible range.