Wide-angle and polarization-insensitive THz absorber with switchable broadband–multiband modes

Abstract The rapid expansion of terahertz (THz) technology is still hampered by the lack of tunable absorbers that combine wide spectral coverage with adaptable functionality. Many existing devices operate efficiently only within a narrow frequency window and offer limited control over their operating modes. In this work, we numerically design a multilayer THz metamaterial absorber that integrates vanadium dioxide (VO 2 ) with graphene in a compact architecture. By exploiting the thermally driven phase transition of VO 2 , the structure can be reconfigured between two distinct electromagnetic responses: an ultra-broadband absorption state and a multi-narrowband state. In the broadband configuration, the proposed absorber maintains an absorption higher than 97% throughout the 0.1-10 THz region, corresponding to a fractional bandwidth of 196.04%. When the phase state of VO 2 is switched, the same device exhibits four pronounced absorption resonances at 1.02, 3.57, 6.09, and 9.02 THz. Numerical analysis further shows that the absorber is insensitive to polarization under both TE and TM illumination and preserves high absorption over a broad angular range. These characteristics suggest that the design can serve as a versatile platform for broadband THz spectroscopy and other adaptive THz components where reconfigurable absorption spectra are required.