Tatiana L. Zinenko

Accurate Analysis of Light Scattering and Absorption by an Infinite Flat Grating of Thin Silver Nanostrips in Free Space Using the Method of Analytical Regularization

We study the plane wave scattering and absorption by a flat grating of thin silver nanostrips located in free space, in the visible-light range. The formulation involves generalized boundary conditions imposed on the strip median lines. We use an accurate numerical solution to this problem based on the dual-series equations and the method of analytical regularization. This guarantees fast convergence and controlled accuracy of computations. Reflectance, transmittance, and absorbance as a function of the wavelength and the grating parameters are analyzed. In addition to well-known surface-plasmon resonances, sharp resonances are revealed in the H-polarized scattering near but not equal to the Rayleigh wavelengths of nonzero diffraction orders; in the E-polarized scattering these resonances are not visible. Asymptotic formulas for the frequencies and natural fields of the grating resonances are presented.

Periodicity Matters: Grating or lattice resonances in the scattering by sparse arrays of subwavelength strips and wires.

This article reviews the nature and history of the discovery of high-quality natural modes existing on periodic arrays of many subwavelength scatterers; such arrays can be viewed as specific periodically structured open resonators. These grating modes (GMs), like any other natural modes, give rise to the associated resonances in electromagnetic-wave scattering and absorption. Their complex wavelengths are always located very close to (but not exactly at) the well-known Rayleigh anomalies (RAs), determined only by the period and the angle of incidence. This circumstance has long been a reason for their misinterpretation as RAs, especially in the measurements and simulations using low-resolution methods. In the frequency scans of the reflectance or transmittance, GM resonances usually develop as asymmetric Fano-shape spikes. In the optical range, if a grating is made of subwavelength-size noble-metal elements, then GMs exist together with better-known localized surface-plasmon (LSP) modes. Thanks to high tunability and considerably higher Q-factors, the GM resonances can potentially replace the LSP-mode resonances in the design of nanosensors, nanoantennas, and solar-cell nanoabsorbers.

Surface-Plasmon, Grating-Mode, and Slab-Mode Resonances in the H- and E-Polarized THz Wave Scattering by a Graphene Strip Grating Embedded into a Dielectric Slab

We considered the scattering and absorption of the H and E-polarized plane waves by an infinite flat graphene strip grating placed in a dielectric slab, in the THz range. Accurate numerical treatment was based on the singular integral equations and their projection to specially tailored orthogonal polynomials. The resulting numerical algorithm possessed guaranteed convergence and provided controlled accuracy. Reflectance, transmittance, and absorbance were studied, and the resonances on the surface-plasmon modes, the grating modes, and the slab modes were identified. The grating or lattice modes are caused by the periodicity. Their complex frequencies are extremely close to Rayleigh anomalies and therefore the Q-factors are extraordinarily high, which makes them promising in various applications.

Characterization of CFRP Thermal Degradation by the Polarization-Frequency Reflectometry Method in Subterahertz Frequency Range

We investigate the carbon fiber reinforced plastics (CFRP) thermal degradation using the polarization-frequency reflectometry (PFR) method in subterahertz frequency range. The setup that realizes the PFR method is developed and includes the sample scanning by a quasi-optical wave beam with various polarizations and frequencies. The CFRP thermal degradation can be detected in the 260 °C-300 °C temperature range using the PFR method confidently enough. Applying full-wave simulation of a plane wave scattering from a CFRP sample with the aid of the integral functional technique, we show that the temperature dependence of the reflection coefficient is due to the change of the CFRP filler permittivity.

Integral equations and sophisticated moment method in the scattering of the terahertz plane waves of two polarizations by a grating of graphene strips

The scattering and absorption of the H and E-polarized plane waves by a flat grating of free standing graphene strips is studied in the THz frequency range. We use the Kubo theory to characterize the surface impedance of graphene and reduce the boundary-value problems to the equivalent integral equations, hyper-singular on the H-case and log-singular in the E-case. Then we discretize them using the projection to the set of orthogonal polynomials; in the H-case these polynomials are chosen to perform the analytical regularization. In each case this technique guarantees fast convergence and controlled accuracy of computations. Reflectance, transmittance, and absorbance of graphene-strip gratings are studied as a function of various parameters. In the H-polarization regime, we find the surface-plasmon resonances and small-scale Rayleigh anomalies. In the E-polarization case, there are no plasmons however the Rayleigh anomalies become well observable. These results can be considered as reference ones opening way to the accurate modeling of tunable absorbers and frequency selective surfaces based on the periodically patterned graphene layers.

Method of analytical regularization in terahertz wave scattering and absorption by infinite gratings of graphene strips

The plane wave scattering and absorption by an infinite flat graphene strip grating are studied in the THz range in the H and E-polarization regimes. Accurate numerical treatment is based on the dual series equations and the analytical regularization technique. In the H-polarization case, the dominant feature is the excitation of the surface plasmon resonances on each strip.

Polarization conversion by metamaterial composed of a periodic array of metallic square helixes embedded in a dielectric layer

The problem of the plane-wave scattering from a 3-D metamaterial layer composed of metallic square helixes periodically embedded in a dielectric layer was solved by the full-wave method of integral functionals. It was shown that such a structure is able to rotate the electric-field intensity vector. The increase in the length of the helix makes it possible to achieve almost complete polarization conversion. The polarization conversion has a resonance character.

Plane wave scattering by a double-periodic gyromagnetic layer analyzed by the integral functional method: Full-wave solution

We obtained full-wave numerical solution of the problem of the plane wave scattering by a double-periodic gyromagnetic layer with the aid of the method of integral functionals. Using this technique it we found the layer thicknesses corresponding to nearly total transmission in a very wide range of the angles of plane wave incidence.

Fano-shape grating resonances of 3D infinite double-periodic grating of thin dielectric bricks

We study the plane wave scattering from double periodic dielectric layer located in free space and illuminated by a linearly polarized plane wave. For the problem solution, we use the method of integral functional based on the vector volume integral-differential equations for the equivalent electric and magnetic polarization currents of the assumed periodic medium. Reflectance and transmittance as a function of the normalized wavelength and the grating parameters are analyzed. Extraordinary sharp grating-type resonances are revealed in the TM- and TE-polarized wave scattering near but not equal to the Rayleigh wavelengths of non-zero diffraction orders.

Experimental study of thermal degradation influence on carbon fiber reinforced plastics reflectivity in sub-terahertz frequency range

In this paper, we investigate an ability of the detection of carbon fiber reinforced plastics (CFRP) thermal degradation using polarization-frequency reflectometry method (PFR) in sub-terahertz frequency range (0.1-0.2 THz) for non-destructive testing of the CFRP samples.