Periodic metallic structures are known to support resonant extraordinarytransmission (EOT). When covered with graphene, these structures can beemployed to effectively manipulate the light. In this work, we propose ananalytical circuit model for graphene-covered one-dimensional metallicgratings. By using the circuit theory, we demonstrate that one-dimensionalperiodic array of cut-through slits which are covered by a continuous graphenesheet exhibit tunable EOT resonance whose amplitude, unlike its spectralposition, can be dynamically tuned by varying the Fermi level of graphene. Inthis fashion, it is shown that placing a perfect reflector at the bottom of thegraphene-covered metallic grating results in the realization of agraphene-based absorber. By utilizing the circuit theory, it is illustratedthat perfect absorption in the structure is not exclusive to the TMpolarization, but also the TE polarized plane waves can be completely absorbedby duly adjusting the Fermi level of graphene. Criteria for the enhancedabsorption are accordingly presented. Results of this work may provide a usefultool for designing novel devices based on the graphene-covered metallicgratings such as filters, modulators and efficient absorbers.
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