Polarization-insensitive graphene-based band-notched frequency selective absorber at terahertz

This paper introduces a new polarization-insensitive graphene-based frequency selective absorber (FSA) with a reflective notch designed for terahertz applications. The proposed structure features two absorption bands on either side of a central reflection band. The design composes a lossy frequency selective surface (FSS), a bandstop FSS with a metal backing, and an air spacer between. A wideband absorber structure is developed in the first step, leveraging graphene as an absorbent material in the lossy layer to achieve wideband absorptive characteristics. Subsequently, a reflection band is introduced by integrating a bandstop, lossless FSS layer into the absorber structure. The overall structure demonstrates two distinct absorption bands, characterized by absorptivity exceeding 80% within the frequency ranges of 0.30 to 0.57 and 0.67 to 0.90 THz. Simultaneously, a reflection notch is achieved at 0.60 THz. Extensive simulations assessed the performance of the designed FSA. The proposed structure exhibits stability under oblique incidence up to 40 deg and allows tunable absorption specifications by adjusting the chemical potential of graphene. It is noteworthy that the FSA reflector offers advantages such as eliminating the need for complicated, high-cost 3-D structures and welding of the lumped resistors.