Modeling of dielectric resonator antenna array for retina photoreceptors.

The retina encompasses several cone and rod photoreceptors at fovea region i.e., 90 million cells of rod photoreceptors and 4.

Graphene coated dielectric resonator antenna for modeling the photoreceptors at visible spectrum.

The absorption of light is very important task for retina photoreceptors. Graphene is an energy harvesting material and one of the best models for the electromagnetic wave absorption and its conversion into signals. In this paper, an electromagnetic modeling of human retinal photoreceptors has been presented based on graphene coated material as a receiver antenna.

Graphene hybrid waveguide stimulation using a photoconductive terahertz generator.

Typically, terahertz (THz) surface plasmon polariton (SPP) excitation involves phase-matching engineering and THz plane-wave generation. This requires antennas, lenses, and other optical phase-matching devices. Herein, we demonstrate a novel, to the best of our knowledge, method to excite THz SPPs in graphene directly by using an 800 nm optical pump and a photoconductive source.

Generalized circuit model for all-dielectric narrowband metasurface absorbers.

All-dielectric metasurface absorbers have great potential in many scientific and technical applications. The emerging metasurfaces show strong and versatile capabilities in controlling absorptance, reflectance, and transmittance of electromagnetic waves. In this work, we propose and investigate all-dielectric metasurface absorbers with an equivalent circuit model.

Terahertz bistability and multistability in graphene/dielectric Fibonacci multilayer.

Here, we benefit from the strong nonlinear response of graphene and the rich variety of resonances provided by a graphene/dielectric Fibonacci multilayer to realize bistability and multistability in the terahertz (THz) frequency range. Toward this pursuit, we employ the nonlinear transfer matrix method. We examine the suitability of resonances in the Fibonacci multilayer for the bi/multistability purposes and determine the proper working point.

Nonlinear optics of surface plasmon polaritons in subwavelength graphene ribbon resonators.

We study the propagation characteristics of surface Plasmon polaritons (SPPs) on a patterned graphene sheet incorporating a subwavelength ribbon resonator and a Kerr nonlinear bounding medium (substrate or top cladding) which provides tunable bandpass filtering in the THz regime. We study theoretically and via modeling the tunability of maxima in the transmission spectrum, corresponding to the resonant frequencies of the ribbon resonator, by tuning the graphene Fermi level (via an applied gate voltage) and by altering the intensity of the incident THz wave. We determine the intensity-dependent increase in the refractive index of a Kerr nonlinear medium bounding graphene, via self-phase modulation and via the more efficient process of cross-phase modulation, revealing a noticeable red-shift in the resonant frequencies of the ribbon resonator.

Quasi-phase matching for efficient long-range plasmonic third-harmonic generation via graphene.

We propose and numerically investigate an efficient method for long-range third-harmonic generation (THG) of propagating surface plasmon polaritons (SPP) waves on graphene sheets for nonlinear plasmonic purposes in the terahertz (THZ) gap region of the electromagnetic spectrum via a developed nonlinear finite-difference time-domain technique. We reveal that although extended and unmodulated graphene sheets with low Fermi levels can offer high-conversion efficiency (CE) for SPP THG at short distances, suitable for miniaturized plasmonic circuits, they suffer from inherent absorption loss induced by graphene that noticeably reduces the CE of the THG at long ranges. We suggest a structure benefiting from low Fermi-level graphene regions of strong nonlinear response as oscillators and high Fermi-level ones of low loss as a propagating medium in a periodic manner, which satisfies the quasi-phase matching condition and shows considerable efficiency improvement at long propagation distances.

Highly tunable nanoscale metal-insulator-metal split ring core ring resonators (SRCRRs).

A class of nano-scale wavelength-selective optical filters is proposed where the core of a metal-insulator-metal square ring is replaced with a split-ring core (SRC). The proposed resonator supports split-ring-resonator-like (SRR-like) resonant modes that are characteristics of the structure. These resonant modes are highly adjustable, via the gap size of the split-ring core, over a range of hundreds of nanometers.

Electromagnetic fields near plasmonic wedges.

The behavior of electromagnetic fields near the edge of a plasmonic wedge is investigated. We study the scattering properties, field divergence, and field enhancement near an Au wedge bounded by SiO2 upon illumination by TM-polarized light using hypersingular integral equations, as a function of wavelength, wedge angle, and angle of incidence. The transverse scattered field components show a convergent behavior at wavelengths approaching the surface plasmon energy asymptote (on the corresponding flat Au-SiO2 interface), and become strongly divergent at longer wavelengths.

Selective-mode optical nanofilters based on plasmonic complementary split-ring resonators.

A nanoplasmonic optical filtering technique based on a complementary split-ring resonator structure is proposed. The basic and modal properties of the square-nanoring are studied using the group theory. Degeneracy and non-degeneracy of the possible TM odd- and even-modes are characterized based on the symmetry elements of the ring structure.

Teardrop-shaped surface-plasmon resonators.

A new surface plasmon resonator, in the form of a metal cylinder shaped like a teardrop, is proposed and modeled using hypersingular integral equations. Illuminating the apex of the teardrop along its axis of symmetry with TM-polarised light excites equal-magnitude surface plasmons counter-propagating around its periphery. Interference of these counter-propagating surface plasmons leads to resonant modes having very sharp line-widths (~0.

Electrical beam steering with metal-anisotropic-metal structure.

In this numerical study, we present and demonstrate a compact, electrical plasmonic beam-steering device composed of anisotropic material. The splitting angle can be modulated by the external electric or magnetic field. The physical principle of this phenomenon is evaluated from the phase of surface plasmon polaritons and Fabry-Perot (F-P) resonance in slits.

Power splitters with different output power levels based on directional coupling.

The properties of a wideband photonic crystal power splitter with different output power levels based on directional coupling are investigated numerically with the finite-difference time-domain method. The effects of changing the coupling length and radius of the coupling rods between parallel waveguides on output transmissions are investigated. By further splitting power in each branch a power splitter with four output branches is proposed.