Wideband Polarization Insensitive Tunable Graphene-Supported Terahertz Metamaterial Absorber

Broadband Terahertz (THz) metamaterial absorbers with tunable absorption characteristics have been attracting a lot of attention due to their high demand and utilization in advanced optical systems. Therefore, we propose a single-layer graphene-supported metamaterial absorber with a combination of square, circular and cross-shaped meta-resonators, exhibiting an outstanding absorption of more than 90% from 2.3 THz to 6.4 THz. The overall size of the unit cell is 15 × 15 μm2, which holds graphene-based meta-resonators etched over a lossy dielectric substrate, backed by a 0.2 μm thick gold as a perfect reflector. This design architecture achieves the ultra-broadband absorption features by continuous design evaluation and optimization. The graphene-based metamaterial absorber (GMMA) reveals a polarization-insensitive response, and it also provides above 70% absorption for obliquely incident angles over the large operating bandwidth (2.3-6.4 THz). The polarization conversion ratio (PCR) also approached zero over the wideband of 4.1 THz and its maximum value of 16% was recorded at 4 THz. Furthermore, the amplitude spectra of the proposed GMMA is modulated from 19% to above 90% by stimulating the chemical potential of graphene from 0 eV to 0.7 eV. The simplified design configuration, broadband absorption features, and tunable capability of the GMMA provide the pathway to develop high-speed optical switches, THz detectors, and other opto-electronic devices.