Ultra-Wideband Terahertz Wave Absorber Using Vertically Structured IGIGIM Metasurface

Achieving perfect absorption of electromagnetic waves across a wide range of frequencies is crucial for various applications, including sensing, imaging, and energy capture. In this study, we introduced a new concept for metasurfaces and proposed a six-layer vertically structured IGIGIM metasurface consisting of gold (Au), silicon (Si), graphene (G1), silica (SiO2), a second layer of graphene (G2), and polymethyl methacrylate (PMMA), which demonstrates ultra-wideband absorptance in the terahertz (THz) region. Through theoretical analysis and numerical simulations, we obtained broadband absorptance over 80% with the average absorptance of 92.6% and a bandwidth of 8.22 THz, from 1.78 to 10.0 THz. Whereas, dual broadband absorptance was obtained for above 90% with the bandwidth of 5.63 THz in the two sub-bands of 2.09-3.5 THz and 5.78-10 THz and above 95% with the bandwidth of 3.63 THz in the two sub-bands of 2.32-3.12 THz and 6.35-9.9 THz. Moreover, the proposed structure exhibits a polarization-independent absorption property. Also, it demonstrates a tolerance for the incident angle of 40 degrees, maintaining a wide absorption band. This remarkable feature is attributed to the multiple Fabry-Perot resonance absorptions in the structure. Our study presents a convenient method for designing high-quality terahertz wave absorbers with outstanding broadband absorptance.