Lara Pajewski

Comments on "Scattering by a finite set of perfectly conducting cylinders buried in a dielectric half-space: a spectral-domain solution

An analytical-numerical technique, for the solution of the two-dimensional electromagnetic plane-wave scattering by a finite set of perfectly conducting circular cylinders buried in a dielectric half-space, is presented. The problem is solved for both the near- and the far-field regions, for TM and TE polarizations. The diffracted field is represented in terms of a superposition of cylindrical waves and use is made of the plane-wave spectrum to take into account the reflection and transmission of such waves by the interface. The validity of the approach is confirmed by comparisons with results available in the literature, with very good agreement. The multiple interactions between two buried cylinders have been studied by considering both the induced currents and the scattered field diagrams. Applications of the method to objects of arbitrary cross-section simulated by a suitable configuration of circular cylinders are shown.

Scattering by buried dielectric cylindrical structures

[1] An analytical-numerical technique for the solution of the two-dimensional electromagnetic plane wave scattering by a finite set of dielectric circular cylinders buried in a dielectric half-space is presented. The problem is solved for both the near- and far-field regions, for transverse magnetic and transverse electric polarizations. The scattered field is represented in terms of a superposition of cylindrical waves, and use is made of the plane wave spectrum to take into account the reflection and transmission of such waves by the interface. The validity of the approach is confirmed by comparisons with results available in the literature, with very good agreement, and by self-consistency tests. Applications of the method to objects of arbitrary cross section simulated by suitable configurations of circular cylinders are shown.

Scattering by Perfectly Conducting Circular Cylinders Buried in a Dielectric Slab Through the Cylindrical Wave Approach

An analytical-numerical technique for the solution of the plane-wave scattering problem by a set of perfectly conducting circular cylinders, buried in a dielectric slab, is presented. The problem is solved for both TM and TE polarizations, and for near- and far-field regions. The proposed method expresses the scattered fields in terms of cylindrical waves, and exploits the plane-wave spectrum of a cylindrical function to take into account the reflection and transmission through the planar interfaces. Numerical results are reported and the validity of the approach is confirmed by comparison with results given in the literature, showing a good agreement.

Design of a binary grating with subwavelength features that acts as a polarizing beam splitter

A binary diffractive optical element, acting as a polarizing beam splitter, is proposed and analyzed. It behaves like a transmissive blazed grating, working on the first or the second diffraction order, depending on the polarization state of the incident radiation. The grating-phase profile required for both polarization states is obtained by means of suitably sized subwavelength groups etched in an isotropic dielectric medium. A rigorous electromagnetic analysis of the grating is presented, and numerical results concerning its performances in terms of diffraction efficiency as well as frequency and angular bandwidths are provided.

Scattering by dielectric circular cylinders in a dielectric slab

An analytical-numerical technique for the solution of the plane-wave scattering problem by a set of dielectric cylinders embedded in a dielectric slab is presented. Scattered fields are expressed by means of expansions into cylindrical functions, and the concept of plane-wave spectrum of a cylindrical function is employed to define reflection and transmission through the planar interfaces. Multiple reflection phenomena due to the presence of a layered geometry are taken into account. Solutions can be obtained for both TM and TE polarizations and for near- and far-field regions. The numerical approach is described and the method is validated by comparison with examples given in the literature, with very good agreement. Results are presented for the scattering by a finite grid of three cylinders embedded in a slab.

Fractal two-dimensional electromagnetic bandgap structures

Fractal two-dimensional electromagnetic bandgap (EBG) materials are proposed and studied by means of a full-wave method developed for diffraction gratings. Such technique allows us to characterize, In an accurate and rapidly convergent way, the transmission and reflection properties of periodic fractal structures with an arbitrary geometry in the unit cell. Both polarization cases can be treated. A validation of the employed method is performed through a comparison with theoretical results and experimental data taken from the literature; the convergence properties of our method when applied to fractal EBG materials are checked. In particular, three different fractal EBGs are considered here. Numerical results are reported for the transmission efficiency as a function of the frequency and the incidence angle. Typical effects due to the fractal geometry are observed, like multiband behavior and enlargement of stopbands.

Applications of Ground Penetrating Radar in civil engineering — COST action TU1208

This paper focuses on the use of Ground Penetrating Radar (GPR) in civil engineering. Open issues in this field are identified and desirable advances in GPR technology, application procedures, data processing algorithms and analysis tools, are addressed. European associations, institutes and consortia interested in this topic are mentioned, together with the main relevant international events. The new COST (European COoperation in Science and Technology) Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar” is presented, started in April 2013: this interdisciplinary project offers important research opportunities and will strengthen European excellence in all the fields concerning the success of GPR technique, with a main focus on its applications in civil engineering. Four Working Groups (WGs) carry out the research activities: WGI focuses on the design of innovative GPR equipment, on the building of prototypes, as well as on the testing and optimization of new systems; WG2 focuses on the GPR surveying of pavement, bridges, tunnels and buildings, as well as on the sensing of underground utilities and voids; WG3 deals with the development of electromagnetic forward and inverse scattering methods and of advanced data processing algorithms; WG4 explores the use of GPR in fields different from civil engineering and the integration of GPR with other nondestructive testing techniques. The COST Action TU1208 is still open to the participation of new parties: in this paper, information is provided for scientists and scientific institutions willing to join the Action and participate to its activities.

Short-Pulse Electromagnetic Scattering by Buried Perfectly Conducting Cylinders

In this letter, the electromagnetic scattering problem of a short-pulse plane wave by a finite set of buried perfectly conducting circular cylinders is addressed in the time domain. The described procedure is applicable for arbitrary polarization and for any cylinder size and configuration in both near- and far-field regions. The solution is performed through an angular-spectrum representation of the scattered field. A parametric analysis on the effects of the various geometrical parameters is reported, and numerical results are presented.

Periodic defects in 2D-PBG materials: full-wave analysis and design

In this paper, an accurate and efficient characterization of two-dimensional photonic bandgap structures with periodic defects is performed, which exploits a full-wave diffraction theory developed for one-dimensional gratings. The high convergence rate of the proposed technique is demonstrated. Results are presented for both TE and TM polarizations, showing the efficiencies as a function of wavelength, incidence angle, geometrical and physical parameters. A comparison with other theoretical results reported in the literature is shown with a good agreement. The transmission properties of photonic crystals with periodic defects are studied, investigating the effects of the variation of geometrical and physical parameters; design efficiency maps and formulas are given; moreover, the application of the analyzed structures as filters is discussed.

Spectral domain method for the electromagnetic scattering by a buried sphere

A rigorous method to analyze the electromagnetic scattering of an elliptically polarized plane wave by a sphere buried in a dielectric half-space, is presented. The electric field components of the incident and the scattered monochromatic plane waves are expanded in series of vectorial spherical harmonics, with unknown expansion coefficients. The scattered-reflected and scattered-transmitted fields are computed by exploiting the plane-wave spectrum of the scattered field, considering the reflection and transmission of each elementary plane wave by the interface. The boundary-condition imposition leads to a linear system that returns the unknown coefficients of the scattered field. To achieve a numerical solution, a code has been implemented, and a truncation criterion for the involved series has been proposed. Comparisons with the literature and simulations performed with a commercial software are presented. A generalization of the method to the case of a short pulse scattered by a buried sphere is presented, taking into account the dispersive properties of the involved media.