A Triple Band Polarization Insensitive Graphene-Based Metasurface Absorber in Terahertz Gap

This paper proposes a graphene-based metasurface absorber structure for low, mid, and trailing ranges of terahertz (THz) gap. The unit cell of the structure consists of a patterned graphene layer with simultaneous plus-shaped and swastika-shaped slots grown over a layer of amorphous silicon dioxide ($\mathbf{S i O}_{2}$) backed by a golden layer. The proposed structure offers three absorption bands having bandwidths of 0.83 THz, 0.96 THz and 0.48 THz with respective peaks at 3.03 $\mathrm{THz}, 6.06 \mathrm{THz}$, and 9.93 THz. The four-fold symmetry of the unit cell makes the structure polarization insensitive in nature. The structure offers angular stability for oblique incidents up to $\mathbf{4 0}$ degrees for both TE and TM modes of polarization. The structure is as thin as $\sim \lambda / 14$ concerning the frequency of first peak absorption, and the periodicity of the unit cell is $\sim \lambda / 16.5$ supporting effective homogeneity condition. The structure can be used for future implementable aspects that can apply to sensing, 6G communications and other biomedical applications.