arXiv subjects

G. Berginc

Publications and source records attributed to G. Berginc.

7 recordsLinked to original sources

arXiv2003

Electromagnetic wave scattering from a random layer with rough interfaces I: Coherent field

The problem of an electromagnetic wave scattered from a random medium layer with rough boundaries is formulated using integral equations which involve two kinds of Green functions. The first one describes the wave scattered by the random medium and the rough boundaries, and the second one which corresponds to the unperturbed Green functions describes the scattering by an homogeneous layer with the rough boundaries. As these equations are formally similar to classical equations used in scattering theory by an infinite random medium, we will be able to apply standard procedures to calculate the coherent field. We will use the coherent potential approximation where the correlations between the particles will be taken into account under the quasi-crystalline approximation.

physics.ao-ph↗

arXiv2003

Electromagnetic wave scattering from a random layer with rough interfaces II: Diffusive intensity

A general approach for the calculation of the incoherent intensity scattered by a random medium with rough boundaries has been developed using a Green function formalism. The random medium consists of spherical particles whose physical repartition is described by a pair-distribution function. The boundary contribution is included in the Green functions with the help of scattering operators which can represent any existing theory of scattering by rough surfaces. By using a standard procedure, we derive the integral Bethe-Salpeter equation under the ladder approximation and, by differentiation, the vectorial radiative transfer equation. Furthermore, with the help of our formalism, the boundary conditions necessary to solve the radiative transfer equation are expressed in terms of the scattering operators of the rough surfaces. Finally, using the reciprocity properties of the Green functions, we are able to include the enhanced backscattering contributions to take into account every state of polarization of the incident and the scattered waves.

physics.ao-ph↗

arXiv2003

Effective dielectric constant for a random medium

In this paper, we present an approximate expression for determining the effective permittivity describing the coherent propagation of an electromagnetic wave in random media. Under the Quasicrystalline Coherent Potential Approximation (QC-CPA), it is known that multiple scattering theory provided an expression for this effective permittivity. The numerical evaluation of this one is, however, a challenging problem. To find a tractable expression, we add some new approximations to the (QC-CPA) approach. As a result, we obtained an expression for the effective permittivity which contained at the same time the Maxwell-Garnett formula in the low frequency limit, and the Keller formula, which has been recently proved to be in good agreement for particles exceeding the wavelength.

physics.optics↗

arXiv2001

Backscattering enhancement of an electromagnetic wave scattered by two-dimensional rough layers

The problem of an electromagnetic wave scattering by a slab with two rough boundaries is solved by a small-perturbation method under the Rayleigh hypothesis. In order to obtain a perturbative development, we use a systematic procedure which involves integral equations called the reduced Rayleigh equations. Then we will show for a dielectric slab deposited on a silver film that the backscattering enhancement can be produced by guided waves which interact with the two rough surfaces.

cond-mat↗

arXiv2001

A new application of reduced Rayleigh equations to electromagnetic wave scattering by two-dimensional randomly rough surfaces

The small perturbations method has been extensively used for waves scattering by rough surfaces. The standard method developped by Rice is difficult to apply when we consider second and third order of scattered fields as a function of the surface height. Calculations can be greatly simplified with the use of reduced Rayleigh equations, because one of the unknown fields can be eliminated. We derive a new set of four reduced equations for the scattering amplitudes, which are applied to the cases of a rough conducting surface, and to a slab where one of the boundary is a rough surface. As in the one-dimensional case, numerical simulations show the appearance of enhanced backscattering for these structures.

cond-mat↗

arXiv1999

Verification of a localization criterion for several disordered media

We analytically compute a localization criterion in double scattering approximation for a set of dielectric spheres or perfectly conducting disks uniformly distributed in a spatial volume which can be either spherical or layered. For every disordered medium, we numerically investigate a localization criterion, and examine the influence of the system parameters on the wavelength localization domains.

physics.optics↗

arXiv1997

A Numerical Study of Absorption by Multilayered Biperiodic Structures

We study the electromagnetic scattering by multilayered biperiodic aggregates of dielectric layers and gratings of conducting plates. We show that the characteristic lengths of such structures provide a good control of absorption bands. The influence of the physical parameters of the problem (sizes, impedances) is discussed.

physics.optics↗