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Two approaches to realize a tunable absorber based on patterned graphene metasurface are proposed in this paper. In the first approach, different from available absorption amplitude tunable absorbers, the center frequency of the absorber can be tuned by the surface resistance of the graphene in a wide range while maintaining a large absorption coefficient. The second approach, by implying the stack of graphene as the absorbing layer, can introduce a remarkable shift of the center frequency. These two approaches are theoretically illustrated using equivalent circuits and 3-D full wave simulation. Samples that are optically transparent are also fabricated and measured in a rectangular waveguide. A good correlation between simulation and measurement results is obtained.
Yi et al. (2017) studied this question.