Abstract
A broadband switchable metamaterial absorber is investigated in this paper. The switchable response is achieved by utilizing the phase transition property of vanadium dioxide (VO2) that is thermally controlled. A novel band extension scheme is presented by introducing capacitive coupling effects among the resonators. By exploiting the coupling effect, near octave bandwidth is achieved when referred to an absorptivity of 90%. Further, by integrating the temperature controlled VO2 film into the dielectric layer, the proposed absorber can be switched between a frequency band from 0.32 THz to 0.56 THz and another band from 0.356 THz to 0.682 THz that is achieved by changing the operation temperature. Due to the symmetrical structure, the studied absorber features polarization insensitive and a wide incident angle of up to 50°. The broadband and switchable properties are discussed based on the resonant structure, surface current distributions, electric field distributions and impedance matching. It is noted the presented method can be scaled to other adjacent THz frequency band.
Highlights
Metamaterials have been received considerable attentions from scientific and engineering communities due to the feasibility of artificially designed material properties since the concept was first introduced theoretically [1]
We propose a bandwidth extension method to design the metamaterial absorber
A switchable broadband VO2-based absorber is studied in this paper
Summary
Metamaterials have been received considerable attentions from scientific and engineering communities due to the feasibility of artificially designed material properties since the concept was first introduced theoretically [1]. MODEL the studied switchable broadband absorber is composed of a composite resonant structure made of Tantalum Nitride (TN) on a multi-layer dielectric plate backed with a gold ground plane. While for metallic phase, the permittivity of VO2 in the THz region is described by the Drude model [41]: ε(ω) = ε∞ − ωp2(σ )/(ω2 + iγ ω), where ε∞ is the permittivity at high frequency, ωp2(σ ) is the conductivity dependent plasmon frequency and γ is the collision frequency. The skin depth is negligible compared with the metal thickness, T(ω) = 0 This means the reflection of incident electromagnetic waves directly determines the absorption.
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