Efficient and high-quality absorption enhancement using epsilon-near-zero cylindrical nano-shells constructed by graphene.

This paper presents a detailed scattering analysis of a hollow-core plasmonic-shell cylindrical wire to design an efficient, compact, narrowband, and reconfigurable optical absorber. The shell is formed by a thin graphene material, investigated in its epsilon-near-zero (ENZ) plasmonic region. Compared to the graphene plasmonic resonances in the terahertz(THz)/far-infrared (FIR) frequencies, the ENZ plasmonic resonances offer a blue shift in the operating frequency of the second-order plasmonic resonances by increasing the geometrical dimensions.

Maximizing the forward scattering of dielectric nanoantennas through surface impedance coatings.

In this Letter, we discuss a novel, to the best of our knowledge, approach for designing passive nanoantennas with maximum forward and almost-zero backward scattering. The proposed approach is based on the use of high-index dielectric spheres supporting dipolar magnetic resonances, which are coated by ultra-thin surface impedance coatings. It is shown that, by properly engineering the radius of the coat and its surface reactance, it is possible to introduce an additional electric dipolar resonance and to make this overlap with the magnetic one sustained by the high-index dielectric sphere.

Reconfigurable switching between reflecting/absorbing modes in VO assisted graphene-coated hemispherical dielectric hole arrays.

In this paper, a graphene-coated dielectric hole array is used to design a reconfigurable switchable optical reflector/absorber device. The design benefits from the collective excitation of localized surface plasmon resonances of graphene-coated hole array, providing simpler fabrication fellow and more compact structure with respect to graphene-coated spherical nanoparticle array with similar plasmonic behavior. Geometrical parametric study of the reflecting mode shows that the device has lots of degrees of freedom for spectrum tuning and can highly tolerate fabrication imperfections.

Solar cell design using graphene-based hollow nano-pillars.

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.

Bi-functional tunable reflector/high-Q absorber design using VO assisted graphene-coated cylinder array.

In this paper, a bi-functional tunable reflector/absorber device using an assembly of graphene-coated cylindrical wires, backed by a thermally controlled phase change material, is proposed. The reflection coefficient of the graphene-coated wire-grating manifests multiple resonances, originating from the hybridized excitation of localized surface plasmons in the graphene shells. The first plasmonic resonance (with the order of two), in the free-standing configuration, shows tunable near-perfect reflection while the second plasmonic resonance (with the order of three), in the reflector-backed array, exhibits near-perfect absorption.

Dual polarized engineering the extinction cross-section of a dielectric wire using graphene-based oligomers.

In this paper, graphene-coated spherical nanoparticles are arranged around an infinite length dielectric cylinder to enhance its extinction cross-section. Initially, a single longitudinal one-dimensional periodic array is considered in different loci concerning the transverse electric (TE) incident plane wave. It is observed that regardless of the position of the particles, the extinction cross-section of the dielectric cylinder is considerably enhanced with respect to the bare one.

Broadband absorption using all-graphene grating-coupled nanoparticles on a reflector.

In this paper, the hybridized localized surface plasmon resonances (LSPRs) of a periodic assembly of graphene-wrapped nanoparticles are used to design a nanoparticle assisted optical absorber. Bandwidth enhancement of this structure via providing multiple types of plasmonic resonances in the associated unit cell using two densely packed crossly stacked graphene strips is proposed. The designed graphene strips support fundamental propagating surface plasmons on the ribbons, and gap plasmons in the cavity constructed by the adjacent sections.

Broadband/multiband absorption through surface plasmon engineering in graphene-wrapped nanospheres.

In this paper, a thin film constructed by a periodic assembly of graphene-wrapped particles with spherical geometry has been proposed as a polarization-insensitive reconfigurable perfect absorber. The performance of the proposed structure is based on the cooperative excitation of the quadrupole localized surface plasmons on graphene shells. By sweeping the quality of graphene shells, it is recognized that the low-quality graphene material is the best choice for the absorber design.

Broadband continuous/discrete spectrum optical absorber using graphene-wrapped fractal oligomers.

In this paper, a second-order fractal oligomer constructed by graphene-coated cylindrical nano-rods is proposed as the unit cell of a wideband optical absorber. Nano-rods have resided on a dielectric substrate with a thick metallic mirror. The fractional bandwidth of the designed structure is 88.

Multi-frequency near-field enhancement with graphene-coated nano-disk homo-dimers.

In this paper, a 3D sub-wavelength graphene-coated nano-disk dimer (GDD) is proposed for multi-frequency giant near-field enhancement. We observed that the dual-band operation originates from the excitation of hybridized localized surface plasmons on top and bottom faces of the disks along with the mutual coupling from the adjacent particle. Due to the sub-wavelength nature of the disks, the excited localized surface plasmons on the sidewalls are weak but they still can affect the dual operating bands.

Dyadic analysis of a cylindrical wire consisting of a cover with fully-populated surface conductivity tensor.

Dyadic Green's function for a monolayer cylinder consisting of a cover with fully-populated surface conductivity tensor is formulated in this paper. Cylindrically wrapped densely packed graphene strips behaving as a hyperbolic meta-surface and arbitrary shaped graphene patterns supporting magneto-plasmons are investigated as two special cases. Closed-form approximate formulas based on effective medium theory (EMT) are available for the surface conductivity of the former and the latter can be analyzed by the effective tensor surface conductivity extraction by means of the finite element method (FEM).