Novel Plasmonic Metamaterials Based on Metal Nano-Hemispheres and Metal-Dielectric Composites

Abstract

We introduce a groundbreaking plasmonic metamaterial, the Nano-Hemisphere on Hyperbolic Metamaterial (NHoHMM), which involves the fabrication of Ag nano-hemispheres on a multilayered Ag/SiO2 structure, achieved solely through sputtering and heat treatment. Finite Difference Time Domain (FDTD) simulations unveil the intriguing slow propagation of the localized electric field, where light travels at only 1/40th of its usual speed within this structure. These simulations reveal distinctive sharp absorption peaks in the visible spectrum, attributed to surface plasmon resonance. In practical experiments, the NHoHMM structure, characterized by random Ag nano-hemispheres, exhibits broad absorption peaks spanning the visible range, rendering it a versatile broadband optical absorber. For comparison, the optical properties of the Ag nano-hemispheres on a nanocermet (NHoNC) structure were analyzed through simultaneous sputtering of Ag and SiO2 followed by heat treatment. Simulations employing effective medium theory and the transfer matrix method demonstrate variable optical properties dependent on the Ag filling ratio in the nanocermet structure. The results obtained differ from the spectra of the NHoHMM structure; thus, it is concluded that in the NHoHMM structure, the calculated multi-peaks are broadened due to the inhomogeneity of the nano-hemispherical structure’s size, rather than the metal/dielectric multilayer structure being altered by the heat treatment.