A high-performance terahertz absorber based on synthetic-patterned vanadium dioxide metamaterials

Abstract

In this paper, we designed a terahertz absorber based on vanadium dioxide (VO2) with tunable and ultra-broadband characteristics. The absorber is composed of four identical synthetic VO2 patterns, the dielectric...

Tunable ultra-broadband terahertz metamaterial absorber based on vanadium dioxide strips

“…According to the impedance matching theory, a metamaterial structure perfectly absorbs the incident electromagnetic radiation when its complex effective wave impedance is matched to that of the wave impedance of the environment. 31,38 Hence, when the total reectance R(u) of the structure approaches zero (A(u) approaches 1), the wave impedance tends to match that of the free space. The relative impedance can be calculated by the following expression…”

“…According to the impedance matching theory, a metamaterial structure perfectly absorbs the incident electromagnetic radiation when its complex effective wave impedance is matched to that of the wave impedance of the environment. 31,38 Hence, when the total reflectance R ( ω ) of the structure approaches zero ( A ( ω ) approaches 1), the wave impedance tends to match that of the free space. The relative impedance can be calculated by the following expressionwhere r = S 11 , t = S 21 are complex reflection and transmission coefficients, is the effective impedance of the metamaterial structure, μ and ε are the effective complex magnetic permeability and dielectric permittivity of the absorber, respectively, and Z 0 ≈ 377 Ω is the wave impedance of air.…”

“…Particularly, VO 2 can undergo reversible phase transition from an insulator phase at the room-temperature to a ‘poor’ metallic phase at characteristic temperatures of ∼65–75 °C. The complex dielectric permittivity of VO 2 in its metallic phase in the THz spectrum can be described according to Drude model, 31 where ε ∞ is the high-frequency permittivity, ω p ( σ ) is the conductivity-dependent plasma frequency, γ is the collision frequency, ω p ( σ 0 ) = 1.4 × 10 15 rad s −1 and σ 0 = 3 × 10 5 S m −1 . The real (black, left axis) and imaginary (red, right axis) part of the dielectric permittivity of the VO 2 in its metallic phase at THz frequencies are shown in inset of Fig.…”

“…The real (black, left axis) and imaginary (red, right axis) part of the dielectric permittivity of the VO 2 in its metallic phase at THz frequencies are shown in inset of Fig. 1 , where experimentally derived values for the high-frequency permittivity, plasma frequency and damping factor were used: 31 σ = 2 × 10 5 S m −1 , ω p = 1.14 × 10 15 rad s −1 , and γ = 5.75 × 10 13 rad s −1 . It is seen that for the chosen conditions, the real part of the dielectric permittivity of VO 2 is negative indicating its metallic nature.…”

“…Consequently, by controlling the temperature, it is possible to change the conductivity of VO 2 in a wide range, which gives wide control over metamaterials. 30,31…”