Ultra-thin polarization independent broadband terahertz metamaterial absorber

In this work, we present the design of a polarization independent broadband absorber in the terahertz (THz) frequency range using a metasurface resonator. The absorber comprises of three layers, of which, the top layer is made of a vanadium dioxide (VO₂) resonator with an electrical conductivity of σ = 200000 S/m; the bottom layer consists of a planar layer made of gold metal, and a dielectric layer is sandwiched between these two layers. The optimized absorber exhibits absorption greater than 90% from 2.54-5.54 THz. Thus, the corresponding bandwidth of the designed absorber is 3 THz. Further, the thermal tunable absorption and reflection spectra have been analyzed by varying the electrical conductivity of VO₂. The impact of the various geometrical parameters on the absorption characteristics has also been assessed. The physics of generation of broadband absorption of the proposed device has been explored using field analysis. Finally, the absorption characteristics of the unit cell has been studied for various incident and polarization angles.