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In this paper, the full solar spectrum coverage with an absorption efficiency above 96% is attained by shell-shaped graphene-based hollow nano-pillars on top of the refractory metal substrate. The material choice guarantees the high thermal stability of the device along with its robustness against harsh environmental conditions. To design the structure, constitutive parameters of graphene material in the desired frequency range are investigated and its absorption capability is illustrated by calculating the attenuation constant of the electromagnetic wave. It is observed that broadband absorption is a consequence of wideband retrieved surface impedance matching with the free-space intrinsic impedance due to the tapered geometry. Moreover, the azimuthal and longitudinal cavity resonances with different orders are exhibited for a better understanding of the underlying wideband absorption mechanism. Importantly, the device can tolerate the oblique incidence in a wide span around 65°, regardless of the polarization. The proposed structure can be realized by large-area fabrication techniques.

Graphene-coated spherical nanoparticles are proposed as the unit cells of a single negative (SNG) meta-surface at infrared frequencies. To derive the effective permittivity of the meta-surface, each graphene layer is represented as a thin shell with complex conductivity calculated by the Kubo formulas. Later, based on the modified Mie Lorenz coefficients of the particle, electric polarizability of the unit cell is obtained, to be used in the Clausius–Mossotti effective medium formulation. The proposed structure has lower optical losses in comparison to its noble metal counterparts and it is tunable by varying the bias voltages of graphene shells. Moreover, material and geometrical parameters of the particles along with the filling fraction of the meta-surface are other parameters for the control of the optical response in the target frequency. A deep sub-wavelength tunable perfect reflector is considered as an instance. Two possible applications of the designed reflector are in lenses and semiconductor laser cavities, as a promising replacement to Bragg reflectors.

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Comb-like behavior of the multilayered graphene wrapped nanotubes in multiple scattering channels is investigated and utilized to design a structure for simultaneous super-scattering and super-cloaking. The underlying physics of the proposed structure is studied quantitatively by geometric interpretation through the associated planar structure based on the Bohr model and Foster's theorem. We observed that due to the presence of multiple dispersion bands in the planar counterpart, each cylindrical scattering Mie coefficient fulfills the resonance and invisibility conditions multiple times, depending on the selected number of layers. By refining the material and geometric parameters for the specified number of layers, resonances and zeros of the first two scattering terms are coincided simultaneously to observe super-scattering and super-cloaking, respectively. The proposed structure has lots of degrees of freedom to control the response in the operating frequency.