All-dielectric terahertz ultra-wideband absorber based on square ring and double H-type

Abstract In this paper, an ultra-broadband THz absorber based on square ring and double H-type of fully dielectric doped silicon is proposed. The proposed structure demonstrates a numerically verified ultra-broadband absorption efficiency exceeding 90%, spanning the frequency range from 0.978 to 6.37 THz, and a relative bandwidth of 146.76%. It features polarization-independent and wide-angle absorption, with contour plots showing uniform absorptivity across TE and TM polarization modes, and minimal variation within a polarization angle range of 0–90°. Angular stability analysis reveals >90% absorption up to 40° (TE mode) and >95% absorption up to 70° (TM mode), enabled by synergistic electromagnetic resonances and optimized impedance matching. The equivalent circuit model further illustrates the ultra-wideband strong absorption characteristics of the proposed absorber. Electromagnetic field analysis identifies multi-modal coupling mechanisms: low-frequency electric dipole resonances in the square ring, magnetic dipole interactions at structural interfaces, and high-order multipole resonances from the double H-type elements. Parametric studies reveal structural tolerance, showing broadband performance persists despite ±20% variations in critical dimensions. The proposed absorber offers higher absorption bandwidth and relative bandwidth ratios, along with thinner thicknesses compared to existing terahertz absorbers. As a result, it demonstrates significant potential for applications in terahertz imaging and other technological fields.