Tunable strong circular dichroism in a non-chiral metallic metasurface integrated with graphene

In this paper, we propose a non-chiral metasurface using an array of V-shaped silver nanostructures surrounded by two graphene sheets to obtain a tunable strong circular dichroism. The position of peaks and dips in the dichroism spectrum depends on the Fermi energy of graphene and can be tuned by changing Fermi energy. For Fermi energies larger than a specific value, stronger tunable circular dichroism is observed. Due to the occurrence of circular dichroism in the near-infrared region, the strong dichroism results from the excitation of surface plasmon in the V-shaped silver nanostructures, not surface plasmon polaritons in the graphene sheets. In addition, the observed tunability is attributed to the dependence of plasmon resonance frequency of silver nanostructures on the surrounding graphene sheets.