A proposal for a multi-functional tunable dual-band plasmonic absorber consisting of a periodic array of elliptical grooves

In this paper, a tunable plasmonic absorber composed of an elliptically grooved metallic film sandwiched between two dielectric layers is presented. To understand the optical response of the structure, its absorption spectrum and resonance modes profiles are numerically calculated using computer simulation technology microwave studio. It is shown that the proposed device can provide two absorption peaks, in the near-infrared region, with absorption coefficients dependent upon the polarization angle of the incident light. Therefore, using a Faraday rotator and applying a variable external magnetic field, the device can be converted into a tunable magneto-optic modulator. From a different point of view, the proposed device is applicable as a sensor to measure mechanical rotations from 0 to 90 degrees. Besides, it is discussed that by adding a graphene layer to the structure, a tunable dual band modulator is realized, by which two absorption bands can be adjusted independently. Simulation results show that modulations of absorption per graphene Fermi energy, about 73.33% eV−1 and 69.54% eV−1 are achieved for the first and the second peaks, respectively. Taking advantage of the above mentioned effects, the proposed device can be used in several applications including magneto-optic modulation, rotation detection, electro-optic modulation and spectral selective tunable absorption.