Ultrathin Broadband Terahertz Metamaterial Absorber Based on Multimode Spoof Localized Surface Plasmon Resonators

Terahertz (THz) metamaterial absorbers (MAs) exhibit significant potential in imaging, communication, sensing, and energy harvesting. For these applications, achieving broadband absorption within an ultrathin profile is crucial. However, realizing this objective while preserving high performance remains a key challenge. In this work, a compact THz MA based on a four‐lobed fan‐shaped corrugated structure supporting spoof localized surface plasmons is presented. The design of the four‐lobed structure facilitates multiresonance coupling, while the use of indium tin oxide for both the patterned structure and ground plane introduces ohmic loss. The proposed design achieves over 90% absorption from 0.75 to 2.16 THz, corresponding to a relative bandwidth of 97%, with a thickness of only 25 μm (relative thickness of 0.067, where is the wavelength at 0.75 THz). The absorber maintains stable performance for both transverse electric and transverse magnetic (TM) polarizations under oblique incidence angles up to ±60°, indicating strong angular and polarization robustness. These results may stimulate further advancements in the development of compact and optically transparent absorbers that combine broadband operation with minimal thickness, thereby enabling new possibilities for practical THz devices.