Pixelated slot-based dual-broadband tunable graphene metasurface absorber design through excitation of coupled modes in terahertz regime

This work presents a dual-broadband metasurface absorber (DBMSA) design inspired by the pixel-based slot patterning of the top graphene sheet (Gpat). Complimentary design procedure using slots ensures an inbuilt DC connection among graphene patterns, which makes tuning of chemical potential (mu c) highly practical. A DBMSA provides an absorptivity (A(f)) >= 90 % from 4.46 to 5.6 THz (22.66 %) in the lower band and from 7.52 to 8.68 THz (14.32 %) in the upper band. At the same time, variation in mu c (Top) from 0.5 to 1 eV leads to the coverage of an ultra-wideband (UWB) terahertz (THz) spectrum from 3.62 to 9.1 THz with A(f) >= 90 % due to the overlapping of bands. The absorber is polarization-insensitive due to the symmetricity in the design of the unit cell and provides stable A(f) for incidence angle <= 60 degrees under both transverse magnetic and electric polarization. The DBMSA is compact and ultra-thin, having periodicity and thickness of lambda 0/6.72 and lambda 0/26.9, respectively. The developed ECM model closely predicts the working principle of the metasurface. In conclusion, the proposed DBMSA can be used for several applications in the THz gap regime, such as THz shielding, radar cross-section (RCS) reduction, sensing, imaging, etc.