Broadband polarization-insensitive terahertz absorber based on Ta₂O₅ snowflake-like structure

Abstract In this paper, an ultra-broadband tantalum pentoxide (Ta 2 O 5 ) all-dielectric metamaterial absorber is proposed from the far-infrared to the terahertz range, which exhibits polarization-insensitive and wide-angle characteristics. The absorber consistently demonstrates an impressive absorption rate exceeding 90% within the frequency range from 1.1 THz to 20 THz. Such an absorber can have a bandwidth and relative bandwidth ratio of 18.9 THz and 179.15%. We employ an equivalent circuit model to simulate the performance of the absorber using transmission line theory, which facilitates near-perfect absorption by finely tuning the geometrical parameters of the structure to match the input impedance with that of free space. Detailed calculations and analyses of the electric and magnetic field distributions, as well as power loss density, are presented to clarifying the underlying mechanisms of absorption. The design of the proposed absorber inherently provides insensitivity to polarization angles and sustains superior absorption efficiency at substantial incidence angles. An exhaustive exploration of the influence of structural variations on the performance of the absorber has been conducted. Looking ahead, the proposed absorber can be potential application in enhanced terahertz imaging, terahertz communication systems, novel energy harvesting solutions and broad scientific research endeavours.