Vakhtang Jandieri

MODEL COMPUTATIONS OF ANGULAR POWER SPECTRA FOR ANISOTROPIC ABSORPTIVE TURBULENT MAGNETIZED PLASMA

Electromagnetic waves scattering in turbulent anisotropic collision magnetized ionospheric plasma is investigated using complex geometrical optics approximation. Correlation function of the phase fluctuations of scattered radiation is obtained taking into account both electron density and magnetic fields fluctuations. The features of the angular power spectrum of scattered radiation are investigated analytically and numerically. The expressions of broadening of the spatial spectrum have been obtained for both powerlaw and anisotropic Gaussian correlation functions of electron density

Depolarization of Metric Radio Signals and the Spatial Spectrum of Scattered Radiation by Magnetized Turbulent Plasma Slab

The mutual correlation function of the phase ∞uctuations of scattered ordinary and extraordinary waves by the magnetized plasma slab with electron density ∞uctuations and the variance of the Faraday angle is calculated by the perturbation method. Analytical expression of broadening of the spatial spectrum of scattered radiation is obtained for arbitrary ∞uctuation spectrum. Numerical calculations are carried out for the anisotropic Gaussian ∞uctuation spectrum at difierent anisotropy factor and the angle of inclination of prolate irregularities with respect to the external magnetic fleld. Isolines of the normalized root mean square deviation of the Faraday angle nonlinearly depends on the angle of inclination of prolate irregularities and increases in proportion to the anisotropy factor; two receiving antennas are located in orthogonal planes. It is shown that the broadening of the spatial spectrum of scattered electromagnetic waves

PECULIARITIES OF SPATIAL SPECTRUM OF SCATTERED ELECTROMAGNETIC WAVES IN ANISOTROPIC INHOMOGENEOUS MEDIUM

Features of spatial power spectrum (SPS) of scattered radiation in a randomly inhomogeneous medium with strongly prolated anisotropic inhomogeneities of dielectric permittivity are investigated. In single scattering approximation, it has been shown that a pronounced gap along a direction of prolate inhomogeneities appears in SPS. Features of SPS of multiple scattered waves at oblique illumination of a boundary of randomly-inhomogeneous medium with prolate irregularities have been analytically studied using smooth perturbation method taking into account diffraction effects. Numerical calculations have shown that with an increase of a distance passing by 192 Gavrilenko et al. the wave in random media, SPS has a double-peaked shape and a gap substantially increases. Its maximum is slightly changed and the width is broadening. The results have been obtained analytically for the first time and could find extensive practical application in optics and be useful in development of principles of remote sensing of random media.

Coupled-mode analysis of contra-directional coupling between two asymmetric photonic crystal waveguides

A self-contained coupled-mode theory for the coupled two asymmetric photonic crystal waveguides (PCWs) is presented. The first-order coupled-mode equations are derived under a weak coupling assumption. The coupling coefficients are obtained systematically by a matrix calculus using the modal solutions of each PCW in isolation. The coupled-mode equations are solved for contra-directional coupling between two asymmetric PCWs formed by a hexagonal lattice of circular air holes in a dielectric medium. The power transmission spectra at different output ports of the coupled PCWs are investigated. It is shown that the self-contained coupled-mode analysis is useful to characterize a peculiar feature of the contra-directionally coupled PCWs as a drop filter.

Linear Amplification of Optical Signal in Coupled Photonic Crystal Waveguides

We introduce a weakly coupled photonic crystal waveguide as a promising and realistic model for all-optical amplification. A symmetric pillar type coupled photonic crystal waveguide consisting of dielectric rods periodically distributed in a free space is proposed as all-optical amplifier. Using, the unique features of the photonic crystals to control and guide the light, we have properly chosen the frequency at which only one mode (odd mode) becomes the propagating mode in the coupled photonic crystal waveguide, whereas another mode (even mode) is completely reflected from the guiding structure. Under this condition, the all-optical amplification is fully realized. The amplification coefficient for the continuous signal and the Gaussian pulse is calculated.

Efficient and rigorous analysis of leaky modes in 2-D EBG guiding structures

Full-wave numerical approach for the analysis of leaky modes in periodic and bandgap structures composed of two-dimensional cylindrical inclusions has been proposed. A self-contained formulation is developed that uses a fast and accurate calculation of the lattice sums, which allows us for an appropriate choice of the spectral determination for each spatial harmonic. We analyze numerically a periodic chain composed of dielectric rods. Phase and attenuation constants are calculated and compared with those obtained by Fourier series expansion method with perfectly matched layers. A very good agreement is observed in a wide frequency range, while the computation time of the proposed approach is much faster.

Analysis of wave guidance by periodic chain of square rods using fourier series expansion method with PML

Modal analysis of infinite periodic chain composed of a square scatterer within the unit cell has been analyzed using the Fourier series expansion method combined with PML. Phase constant and attenuation constant associated with the guiding and leaky modes, respectively have been efficiently calculated.

Realization of All-Optical Digital Amplification in Coupled Nonlinear Photonic Crystal Waveguides

In this conceptual study, all-optical amplification of the light pulses in two weakly coupled nonlinear photonic crystal waveguides (PCWs) is proposed. We consider two adjacent PCWs, which consist of line defects in a 2D square lattice of periodically distributed circular rods made from dielectric material with Kerr-type nonlinearity. Dispersion diagrams of the PCW’s symmetric and antisymmetric modes are analyzed using a recently developed analytical formulation. The operating frequency is properly chosen to be located at the edge of the PCW’s dispersion diagram (i.e., adjacent to the photonic crystals low-energy band edge), where in the linear case no propagation modes are excited. However, in case of a nonlinear medium when the amplitude of the injected signal is above some threshold value, solitons are formed propagating inside the coupled nonlinear PCWs. The near field distributions of the propagating light pulse inside the coupled nonlinear PCWs and the output power of the received signal are numerically studied in a detail. A very good agreement between the analytic soliton solution based on the nonlinear Schrödinger equation and numerical result is obtained. Amplification coefficients are calculated for the various amplitudes of the input signals. The results vividly demonstrate the effectiveness of the weakly coupled nonlinear PCWs as an all-optical digital amplifier.

Analysis of Post-Wall Waveguides and Circuits Using a Model of Two-Dimensional Photonic Crystals

A semi-analytical method to analyze post-wall waveguides and circuits based on the model of two-dimensional photonic crystals formed by layered periodic arrays of circular cylinders is presented. The propagation constant of the fundamental TE mode, the attenuation constant due to the leakage loss and the effective width of an equivalent rectangular waveguide are calculated. Using the concept of the effective width, the original structure is replaced by an equivalent rectangular structure. When additional metallic posts are loaded in the rectangular waveguide, functional post-wall waveguide-based passive circuits are formed. The S-parameters of the post-wall circuits, which act as bandpass filters, are calculated using the image theory combined with the lattice sums technique.

Rigorous Analysis of Electromagnetic Scattering by Grating of Plasmonic Nanorods Coupled to Magneto-Optical Slab

A rigorous self-contained formulation for analyzing electromagnetic scattering by a grating of plasmonic nanorods (Ag) coupled to a magneto-optical slab is presented. Bi-substituted gadolinium iron garnet is considered as the magneto-optical material. We measured the dielectric permittivity of the iron garnet and utilized the experimental data in our analyses. The method uses the Lattice Sums technique combined with the generalized reflection matrix approach. Using the method, the spectral response in reflectance as well as near-field distributions at resonance wavelengths have been numerical studied. Special attention has been paid to the coupling mechanism between the plasmonic grating and the magneto-optical slab. Physical insight is given to the strong field enhancement inside the magneto-optical material due to coupling with the plasmonic grating. Generalization of the method to the multilayered sandwiched structures, where the metal layer supporting surface plasmons is in contact with a layer possessing magnetically induced anisotropy, is straightforward. Such a combination enables one to achieve a multifold increase in sensitivity when compared with a system having just one nonmagnetic metal layer.