Interfacial Interaction in MeO/MWNTs (Me-Cu, Ni) Nanostructures as Efficient Electrode Materials for High-Performance Supercapacitors.

Due to their unique physical and chemical properties, complex nanostructures based on carbon nanotubes and transition metal oxides are considered promising electrode materials for the fabrication of high-performance supercapacitors with a fast charge rate, high power density, and long cycle life. The crucial role in determining their efficiency is played by the properties of the interface in such nanostructures, among them, the type of chemical bonds between their components. The complementary theoretical and experimental methods, including dispersion-corrected density functional theory (DFT-D3) within GGA-PBE approximation, scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman, X-ray photoelectron, and X-ray absorption spectroscopies, were applied in the present work for the comprehensive investigation of surface morphology, structure, and electronic properties in CuOx/MWCNTs and NiO/MWCNTs.

Delocalized Electric Field Enhancement through Near-Infrared Quasi-BIC Modes in a Hollow Cuboid Metasurface.

The two main problems of dielectric metasurfaces for sensing and spectroscopy based on electromagnetic field enhancement are that resonances are mainly localized inside the resonator volume and that experimental Q-factors are very limited. To address these issues, a novel dielectric metasurface supporting delocalized modes based on quasi-bound states in the continuum (quasi-BICs) is proposed and theoretically demonstrated. The metasurface comprises a periodic array of silicon hollow nanocuboids patterned on a glass substrate.

Multifunctional THz Graphene Antenna with 360 Continuous -Steering and -Control of Beam.

A novel graphene antenna composed of a graphene dipole and four auxiliary graphene sheets oriented at 90∘ to each other is proposed and analyzed. The sheets play the role of reflectors. A detailed group-theoretical analysis of symmetry properties of the discussed antennas has been completed.

Graphene THz filter-switch dividers based on dipole-quadrupole and magneto-optical resonance effects.

We propose and analyze a multifunctional THz graphene-based component with graphene elements placed on a dielectric substrate. The structure of the device consists of a disc shaped resonator coupled to three graphene waveguides that excite the dipole or quadrupole resonance of surface plasmon polaritons in the resonator. The graphene resonator can be magnetized by a DC magnetic field.

Dielectric-Loaded Waveguides as Advanced Platforms for Diagnostics and Application of Transparent Thin Films.

An alternative approach to classical surface plasmon resonance spectroscopy is dielectric-loaded waveguide (DLWG) spectroscopy, widely used in the past decades to investigate bio-interaction kinetics. Despite their wide application, a successful and clear approach to use the DLWGs for the one-step simultaneous determination of both the thickness and refractive index of organic thin films is absent in the literature. We propose here, for the first time, an experimental protocol based on the multimodal nature of DLWGs to be followed in order to evaluate the optical constants and thickness of transparent thin films with a unique measurement.

Graphene-based multifunctional three-port THz and long-wave infrared components.

Two graphene-based T-shaped multifunctional components for THz and long-wave infrared regions are proposed and analyzed. The first component can serve as a divider, a switch, and a dynamically controllable filter. This T-junction presents a circular graphene resonator and three graphene waveguides with surface plasmon-polariton waves connected frontally to the resonator.

Dynamically controllable graphene terahertz splitters with nonreciprocal properties.

Two novel graphene-based nonreciprocal four-port splitters for the terahertz region are proposed. The input power is divided between two output ports, whereas the input port is isolated from the output ports due to the presence of the fourth port. The splitters consist of a circular graphene resonator and four graphene waveguides coupled to the resonator.

Ultrawideband graphene three-port circulator for THz region.

The suggested circulator is formed by a concave pattern graphene junction and three waveguides symmetrically connected to it. The graphene is supported by SiO/Si layers. The circulation behavior is based on the nonsymmetry of the graphene conductivity tensor which appears due to magnetization by a DC magnetic field applied normally to the graphene plane.

Two-color surface plasmon resonance nanosizer for gold nanoparticles.

We study the potentialities of a two-color Surface Plasmon Resonance (SPR) spectroscopy nanosizer by monitoring the assembling of a colloidal dispersion of citrate stabilized gold nanoparticles (AuNPs) on SiO surface. When the AuNPs/water composite's optical density layer is negligible and the electron mean-free path limitation is taken into account in the AuNPs' dielectric constant;s formulation, the surface density σ of the nanoparticle array and the statistical mean size of the nanoparticles can be straightly determined by using two-color SPR spectroscopy in the context of Maxwell's Garnett theory. The optical method, demonstrated experimentally for AuNPs with a nominal mean diameter of 15 nm, can, theoretically, be extended to bigger nanoparticles, based on a simple scaling relation between the extinction cross section of the single nanoparticle σ and the surface density σ.

Limits of the Effective Medium Theory in Particle Amplified Surface Plasmon Resonance Spectroscopy Biosensors.

The resonant wave modes in monomodal and multimodal planar Surface Plasmon Resonance (SPR) sensors and their response to a bidimensional array of gold nanoparticles (AuNPs) are analyzed both theoretically and experimentally, to investigate the parameters that rule the correct nanoparticle counting in the emerging metal nanoparticle-amplified surface plasmon resonance (PA-SPR) spectroscopy. With numerical simulations based on the Finite Element Method (FEM), we evaluate the error performed in the determination of the surface density of nanoparticles when the Maxwell-Garnett effective medium theory is used for fast data processing of the SPR reflectivity curves upon nanoparticle detection. The deviation increases directly with the manifestations of non-negligible scattering cross-section of the single nanoparticle, dipole-dipole interactions between adjacent AuNPs and dipolar interactions with the metal substrate.

Two-dimensional photonic-crystal-based double switch-divider.

We propose and investigate a new multifunctional component, consisting of a T-junction of three waveguides in 2D photonic crystal with a square lattice. One waveguide is the input port, while the other two serve as output ports. This component can fulfil three functions: First, it can switch OFF the two output ports; second, our component can be used as a 3 dB divider of the input power; and third, it can switch ON any one of the two output ports.

Planar THz electromagnetic graphene pass-band filter with low polarization and angle of incidence dependencies.

We propose and analyze a graphene electromagnetic filter for the terahertz (THz) region. The filter represents a planar square array of graphene elements. A unit cell of the array is formed by two coaxial graphene rings placed on the opposite sides of a thin dielectric substrate.

Magneto-optical resonator switches in two-dimensional photonic crystals: geometry, symmetry, scattering matrices, and two examples.

We discuss different geometrical structures of optical switches based on two-dimensional photonic crystals with hexagonal geometry of the unit cell and a magneto-optical resonator. Transition between the states on and off in these switches is achieved by an external DC magnetic field. The input and output waveguides can be front-front, side-side, or front-side coupled to the resonator and these different types of coupling can lead to different mechanisms of switching.

Possible mechanisms of switching in symmetrical two-ports based on 2D photonic crystals with magneto-optical resonators.

We analyze possible mechanisms of switching in two-ports based on 2D photonic crystals (PhCs) with a magneto-optical resonator. The input and output waveguides can be side or front coupled with the resonator. The resonator operates with a dipole mode.

Optical component: nonreciprocal three-way divider based on magneto-optical resonator.

We suggest and analyze a new compact nonreciprocal optical component based on a magneto-optical (MO) resonator. This component fulfills simultaneously two functions, namely, equal division of the input signal between three output ports and isolation of the input port from output ones. Using group theory, we analyze the scattering matrix of this symmetrical component.

Enhancement of Faraday and Kerr rotations in three-layer heterostructure with extraordinary optical transmission effect.

We theoretically investigate and optimize a multilayer planar structure with enhanced magneto-optical (MO) activity. The extraordinary optical transmission observed in a periodically perforated metal plate with subwavelength holes is used to produce a higher MO activity. We consider a three-layer structure that consists of a dielectric layer placed between the perforated metal and the MO layers.

Compact optical switch based on 2D photonic crystal and magneto-optical cavity.

A compact optical switch based on a 2D photonic crystal (PhC) and a magneto-optical cavity is suggested and analyzed. The cavity is coupled to two parallel and misaligned PC waveguides and operates with dipole mode. When the cavity is nonmagnetized, the dipole mode excited by a signal in the input waveguide has a node in the output waveguide.

Nonreciprocal optical divider based on two-dimensional photonic crystal and magneto-optical cavity.

We suggest and analyze a new nonreciprocal optical device based on two-dimensional photonic crystal and a magneto-optical cavity that simultaneously fulfills two functions: division of the input signal and isolation of the input port from two output ones. At the central frequency, the division of the signal between the output ports is -3 dB and the isolation of the input port from the output ones is about -25 dB. For the level -20 dB of this isolation, the calculated bandwidth is around 100 GHz at the wavelength 1.

Compact three-port optical two-dimensional photonic crystal-based circulator of W-format.

A three-port optical circulator of W-format based on 2D photonic crystal is presented. This circulator is more compact as compared to the known one of the traditional Y-format. The W-circulator does not have rotational symmetry.