A switchable THz absorber, with absorbance more than 90% is proposed, and numerically characterized. The absorber structure is based on metamaterials with unit cells consisting of two patterned graphene layers separated by a 5-nm thick layer of AlO. Numerical results show that when the chemical potential of the top graphene microribbons are tuned by an external variable bias and that of the lower graphene fishnet is kept at μ=0, frequency of the absorption peaks can be tuned as desired, therefore we can have tunable or switchable absorbers.
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