An ultra-broadband infrared absorber using gradient metasurface

Abstract

Metamaterial absorbers (MAs) are one of the important applications of metamaterials, which are artificially constructed plasmonic nanostructures usually based on metal-insulation-metal (MIM), and possess exotic electromagnetic properties that cannon be realized by nature materials [1]. Due to the advantages of perfect absorption and thin thickness, MAs have been attracted much more attentions and made great progress in the past several years [2, 3]. However, the previous demonstrated devices suffered from a limited bandwidth. Here, we propose a metasurface-based absorber by combing four different pentagon patch MIM resonators within a subwavelength period, which demonstrates ultra-broadband absorption in the infrared spectrum. Both the metal and dielectric thicknesses are very thin (<λ/20) and are the same for each resonator of the patchwork. The single-layer absorber demonstrates the broadband absorption of light between 8 and 12 um, with an average absorption of 90%. Furthermore, the double-layer absorber demonstrates an ultra-broadband absorption of light between 5.5 and 13.5 um, with an average absorption of 80%. Figure 1 demonstrates the simulation results of the proposed ultra-broadband absorber. This paves the way to the design of ultra-wideband efficient plasmonic absorbers in the infrared spectrum.