Dual-wavelength active and tunable modulation at telecommunication wavelengths using graphene-metal hybrid metamaterial based on plasmon induced transparency

Abstract

Classic optical systems with a similar response to electromagnetically induced transparency (EIT) have received considerable attention. Plasmonically induced transparency (PIT) response is usually achieved by near-field coupling between resonators’ bright and dark modes. Most PIT structures are based on metamaterials and have a constant near-infrared spectral response; manipulating the PIT spectral response without changing the geometric structure and modifying the substrate or electrical biasing is impossible. A graphene-metal metamaterial structure is proposed to create an active tunable near-IR transparency window. In the proposed two-layer structure, the metal bars act as bright resonators in the upper layer. In the lower layer, the metal nanoribbons act as dark resonators and two sets of bilayer graphene are placed separately below the bright resonators and above the dark resonators. At first, the optimal induced transparency window is obtained by modifying the metal metamaterial’s geometrical parameters. Then, the properties of the generated induced window can be modified by varying the Fermi energies of the used graphene sheets in the hybrid metal-graphene metamaterial. The Fermi energies of the graphene sheets are adjusted by applying a voltage that causes the PIT phenomenon to be actively tunable. The proposed structure can be used as an active modulator in o and c communication bands. The designed modulator allows for 85% and 90% amplitude modulation depths (MD) at about 1307 nm and 1554 nm wavelengths.