Multiband terahertz metasurface absorber using Hilbert fractal

Abstract

Most of the natural materials have very weak interaction with the terahertz (THz) electromagnetic waves. Designing an absorber in the THz range is of considerable interest. We present multiband THz metasurface absorbers formed by the metallic Hilbert fractals separated with a dielectric layer from the metallic ground-plane. Numerical simulations reveal that the absorption spectra of the second-order Hilbert fractal absorber have four absorption bands located at 1.61, 3.41, 4.61, and 5.61 THz with absorption efficiency of 1, 0.97, 0.99, and 0.93, respectively. We also compare three orders of Hilbert fractals as resonant elements and examine the role of different geometrical parameters on the absorption spectra. The proposed absorbers can be readily tuned to desired frequencies for applications, such as imaging, filtering, sensing, and selective thermal emission.