Five layer bi-directionally adjustable perfect metamaterial absorber based on silver gratings with four narrow bands and 1650 nm broadband absorptions

The remarkable performance of metamaterial perfect absorbers in applications such as solar cells, sensors, and photoconversion devices has underscored their progressively important role in diverse areas of scientific and technological development. However, designing perfect absorbers that achieve both narrowband and broadband absorption with relatively simple structures remains a significant challenge. This paper presents a bi-directional metamaterial perfect absorber comprising a silver grating, featuring a specialized structure engineered to simultaneously achieve narrowband and broadband perfect absorption in the same nanostructure. Four distinct absorption peaks are observed when the light source is incident from the grating portion located above the structure, exhibiting absorptivity of 91.8 %, 99.8 %, 94.3 % and 93.2 %. All of these peaks demonstrate favorable sensing performance. In contrast, broadband perfect absorption is observed across the wavelength range of 650–2300 nm when the light source is incident from the bottom planar section of the proposed absorber, exhibiting an average absorption of 95.85 %. Simulation results demonstrate that our designed absorber exhibits excellent narrowband and broadband absorption properties and is simpler and easier to fabricate than other bidirectional absorber materials, suggesting its potential for broader applications compared to traditional absorbers.