A tunable and polarization insensitive wideband THz absorber using a perturbed fractal patterned metasurface augmented with graphene

Abstract In this work a graphene-based perturbed Box fractal-patterned metasurface absorber is proposed for terahertz (THz) sensing applications. The broadband metamaterial absorber is composed of a periodic arrangement of a perturbed Box fractal-patterned graphene top layer on a dielectric substrate (Al2O3) with a gold ground layer (Au) to improve the absorptance. The top graphene layer pattern, evolves by perturbing a second iteration Box fractal structure, which exhibits an increase in the absorptance bandwidth. The detailed evolution of the top graphene pattern is presented. The wideband THz absorption was optimized by tuning the graphene chemical potential of the designed perturbed Box fractal absorber. The absorption spectrum across various polarization conditions indicates that the proposed THz graphene metamaterial absorber (MA) structure remains unaffected by changes in polarization and incident angles. The designed absorber exhibits a broadband absorption above 80% in 5.91-8.87 THz frequency range with a 2.96 THz bandwidth and 2.45 THz for more than 90 % absorption. The absorbance was also obtained by invoking the interference theory model, with close agreement between the theoretical and simulated results. To illustrate the absorber performance efficacy over the band, a 12 × 12 array was modeled and excited with a plane wave.