Optimization of terahertz broadband polarization insensitive metamaterial absorber using bisecting rectangles technique based on quadratic surrogates

In this paper, an optimization algorithm based on bisecting hyperrectangles and constructing quadratic models is exploited to attain the optimal design of a broadband metamaterial absorber (MMA) with small thickness and high absorption in the terahertz (THz) frequency range. The full wave vectorial finite element method is employed along with the introduced algorithm to simulate and optimize the investigated design. The presented absorber comprises of a vanadium dioxide (VO2) metallic layer placed on a lossy polyimide dielectric substrate. Further, the reported design exhibits a broad bandwidth of 2.9 THz where the absorptivity exceeds 90% through a frequency range between 2.43 and 5.33 THz. In addition, the proposed design could obtain polarization insensitive absorption spectrum for the transverse electric (TE) as well as transverse magnetic (TM) polarizations. Furthermore, the absorption spectrum of the suggested absorber could realize high absorptivity (greater than 80%) for the TE and TM polarizations when the wave incident angle is varied from normal incidence to 50°. Therefore, the reported optimization algorithm is highly recommended for THZ broadband MMAs based applications.