Design, simulation, and characterization of THz metamaterial absorber

In recent years a great amount of research has been focused on metamaterials, initially for fabrication of left-handed materials for use in devices such as superlenses or electromagnetic cloaking. Such devices have been developed and demonstrated in regimes from the radio frequency all the way to infrared and near optical frequencies. More recently, it has been shown that, by careful adjustment of the effective permittivity and permeability, near perfect electromagnetic absorbers can be realized. High absorption occurs when transmission and reflection are simultaneously minimized. With some clever tuning of the electric and magnetic responses, the electric and magnetic energy can therefore both be absorbed by the same metamaterial structure. In this work we present the design, simulation and characterization of a novel thin, flexible, polarization insensitive metamaterial absorber. Finite-element simulation results show that this device achieves almost perfect absorption at THz frequencies. Each unit cell of the absorber is made up of two metallic structures separated by a dielectric filler material. The electric response can be tuned by adjusting the geometry of the top metallic electric ring resonator structure. We demonstrate that a rotation about the axis of THz wave propagation at normal incidence does not change the absorption or the resonance frequency by a significant amount. A value of absorption of 99.6 % at a resonance frequency of 0.84 THz can be achieved. We also demonstrate the characteristics of this absorber structure under various THz wave incidence angles, with respect to both the incident electric and magnetic fields.