Edge effects in bistatic measurements of scattering characteristics of material samples.

This work is devoted to studying errors emerging by the edge effects when measuring the reflection coefficient (R) and when finding Brewster angle. The impact of edge effects on the scattering characteristics of planar material samples with different geometries was considered. The method of moments in the FEKO program and analytical calculations using Fresnel formulas are used to study a model material with frequency-independent parameters of the medium. A plane linearly polarized wave falling on the object was studied. For each incidence angle of the wave, the electromagnetic field reflected from the object in the mirror direction was calculated. To calibrate the received signal a reference metal plate of the same size as the size of sample under study was used. To estimate the contribution of the finite-size of the sample in the of reflection coefficient, the simulation results were compared with analytical calculations using Fresnel formulas. The results of the electrodynamic simulation of the characteristics of the model material showed that the position of the sample relative to the polarization of the incident wave does not affect the R value; an increase in Brewster angle depending on the frequency was observed. The reflection coefficient of a square sample with a radar absorbent material (RAM) on a metal substrate was investigated. Measurements of the sample scattering characteristics were carried out in an indoor electromagnetic test bistatic facility (anechoic chamber) in ITAE RAS. The experimental results are in accordance with the calculated data obtained by the method of moments and analytical data. For the sample under study, the value of Brewster angle was not determined due to the fact that this value is outside the measurement range. A significant influence of edge effects on the reflection coefficient of the material sample was revealed, especially for angles closed to Brewster angle.

Laws of reflection and refraction of TE and TM polarization waves on the border of rhombic crystals

The article analytically solves the problem of reflection and refraction of electromagnetic plane waves of different polarization at the boundary of anisotropic half-spaces of rhombic symmetry. Based on the matrix method, the angles of refraction of electromagnetic waves of different polarization, the amplitudes of the reflected and refracted waves, the angles that determine the direction of the group velocities and vectors of the flow of electromagnetic energy, the magnitudes of the flows of electromagnetic energy and their components depending on the direction of the wave vector of the incident wave are determined. The determination of the angles of total internal reflection and the refractive index of electromagnetic waves of different polarization is considered. A significantly different dependence of the kinematic and energy characteristics of electromagnetic waves of different polarization on the anisotropy of the magnetic and dielectric tensors is shown. For electromagnetic waves, the polarization of which is determined by the component of the electric tension vector perpendicular to the wave propagation plane (TE wave), the characteristics of the reflected and refracted waves, the velocity indicatrix, the propagation angles, etc. determined primarily by the components of the magnetic permeability tensor. In the case of electromagnetic waves, when the polarization is determined by the component of the magnetic field (TM wave), perpendicular to the plane of wave propagation, all characteristics depend mainly on the components of the dielectric constant. The validity of the Fresnel formulas for determining the coefficients of reflected and refracted waves at the boundary of anisotropic media of rhombic symmetry is shown. However, in this case, the components of the wave vectors included in the Fresnel formulas are determined by their indicatrices. In addition, it is necessary to take into account the dependence of these components on the angle of refraction in the second medium

New Garnet Films for Magneto-Optical Photonic Crystals

ABSTRACTEpitaxial La3Ga5O12 (LGG) garnet films and Bi3Fe5O12/La3Ga5O12 (BIG/LGG) heteroepitaxial structures have been synthesized on Gd3Ga5O12(GGG, 111) single crystal. LGG films were grown by Pulsed Laser Deposition (PLD) technique whereas rf-magnetron sputtering was used to grow BIG films. We demonstrate LGG is a promising material to be integrated with a giant Faraday rotator Bi3Fe5O12 in magneto-optical photonic crystals. LGG has a lattice constant 12.772 Å that is bigger than that in GGG (12.384 Å) and closer to that in BIG (12.626 Å). Heteroepitaxial Bi3Fe5O12(2μm)/La3Ga5O12(300nm) structures grown on the GGG(111) single crystal show the Faraday rotation as high as 5.74 deg/μm compared to 5.46 deg/μm in BIG/GGG at λ = 655 nm. Fitting LGG reflectivity spectra to Fresnel formulas yields LGG refractive index n = 1.981 compared to 1.963 in GGG at 655 nm. Dispersion of LGG refraction index follows Sellmeier formula n2 = 1 + 2.78/ [1 – (138nm/λ)2] in the range from 400 nm to 1000 nm.