arXiv subjects

Minas Kouroublakis

Publications and source records attributed to Minas Kouroublakis.

5 recordsLinked to original sources

arXiv2026

Frequency-Domain Analysis of Wave Scattering by Spatially Dispersive Metasurfaces Using the Method of Auxiliary Sources

Spatially dispersive metasurfaces exhibit angle-dependent responses that cannot be accurately modeled using conventional local susceptibilities. Extended Generalized Sheet Transition Conditions (GSTCs) have been introduced to account for spatial dispersion by incorporating spatial derivatives of the electromagnetic fields. In this work, these extended GSTCs are integrated into the Method of Auxiliary Sources (MAS), resulting in a meshless simulation framework for the analysis of spatially dispersive metasurfaces. The proposed formulation is developed for infinite planar, finite planar, polygon shaped, and cylindrical metasurfaces, while it is general and also applicable to bianisotropic spatially dispersive metasurfaces. For validation, the numerical examples consider Lorentz-type spatial resonators, consistent with previously published studies. The extended GSTCs are enforced within the MAS via appropriate placement of auxiliary sources. Numerical results are presented for several geometries, including planar, polygonal, semicircular, and cylindrical metasurfaces. The obtained results show very good agreement with previously published data, demonstrating the accuracy and flexibility of the proposed method.

physics.optics↗

arXiv2026

A Time-Domain Method of Auxiliary Sources for Analyzing Transient Electromagnetic Interactions with GSTC-Modeled Metasurfacess

This paper presents a time domain (TD) formulation for modeling the transient electromagnetic response of two-dimensional (2D) metasurfaces using the Method of Auxiliary Sources (MAS) combined with the Generalized Sheet Transition Condition (GSTC). In the proposed approach, the frequency-domain impedance type GSTC is transformed into a causal, convolution-based TD representation and integrated within the MAS formulation. rfaces.

physics.comp-ph↗

arXiv2025

A Time-Domain Method of Auxiliary Sources for Efficient Analysis of Transient Electromagnetic Scattering by Moderately Conductive Cylinders

This paper presents a time-domain implementation of the Method of Auxiliary Sources (MAS) combined with the Standard Impedance Boundary Condition (SIBC) for electromagnetic scattering problems involving cylindrical scatterers with finite but moderate conductivity. The proposed approach focuses on solving the two-dimensional problem using a first-order SIBC, which is valid when the conductivity is sufficiently higher than the maximum spectral frequency times the dielectric permittivity of the scatterer. This regime includes moderately conductive materials--such as carbon-based composites, conductive polymers, and doped dielectrics--that are increasingly used in real-world radio-frequency applications, including wearable electronics, electromagnetic interference shielding, and biomedical sensors. Under the above validity conditions, the interaction between the incident wave and the scatterer is dominated by surface effects, allowing for an efficient and accurate modeling strategy without the need to compute internal fields. The theoretical formulation of the time-domain MAS-SIBC method is developed, followed by extensive numerical testing on various geometries whose cross section is a closed curve. Such geometries include circular, elliptical, super-circular, rounded-triangular, and inverted-elliptical scatterers. A planar geometry is also tested. All results are validated against analytical solutions and commercial frequency-domain solvers, demonstrating the accuracy and practical potential of the proposed method. The findings suggest that time-domain MAS-SIBC offers a promising and computationally efficient approach for modeling scattering from materials even with moderate conductivity.

physics.class-ph↗

arXiv2025

Electromagnetic Multipole Theory for Two-dimensional Photonics

We develop a full-wave electromagnetic (EM) theory for calculating the multipole decomposition in two-dimensional (2-D) structures consisting of isolated, arbitrarily shaped, inhomogeneous, anisotropic cylinders or a collection of such. To derive the multipole decomposition, we first solve the scattering problem by expanding the scattered electric field in divergenceless cylindrical vector wave functions (CVWF) with unknown expansion coefficients that characterize the multipole response. These expansion coefficients are then expressed via contour integrals of the vectorial components of the scattered electric field evaluated via an electric field volume integral equation (EFVIE). The kernels of the EFVIE are the products of the tensorial 2-D Green's function (GF) expansion and the equivalent 2-D volumetric electric and magnetic current densities. We validate the theory using the commercial finite element solver COMSOL Multiphysics. In the validation, we compute the multipole decomposition of the fields scattered from various 2-D structures and compare the results with alternative formulations. Finally, we demonstrate the applicability of the theory to study an emerging photonics application on oligomers-based highly directional switching using active media. This analysis addresses a critical gap in current literature, where multipole theories exist primarily for three-dimensional (3-D) particles of isotropic materials. Our work enhances the understanding and utilization of the optical properties of 2-D, inhomogeneous, and anisotropic cylindrical structures, contributing to advancements in photonic and meta-optics technologies.

physics.optics↗

arXiv2024

Fundamentals of a Null Field Method-Surface Equivalence Principle Approach for Scattering by Dielectric Cylinders

The null-field method (NFM) and the method of auxiliary sources (MAS) have been both used extensively for the numerical solution of boundary-value problems arising in diverse applications involving propagation and scattering of waves. It has been shown that, under certain conditions, the applicability of MAS may be restricted by issues concerning the divergence of the auxiliary currents, manifested by the appearance of exponentially large oscillations. In this work, we combine the NFM with the surface equivalence principle (SEP) and investigate analytically the convergence properties of the combined NFM-SEP with reference to the problem of (internal or external) line-source excitation of a dielectric cylinder. Our main purpose is to prove that (contrary to the MAS) the discrete NFM-SEP currents, when properly normalized, always converge to the corresponding continuous current densities, and thus no divergence and oscillations phenomena appear. The theoretical analysis of the NFM-SEP is accompanied by detailed comparisons with the MAS as well as with representative numerical results illustrating the conclusions.

math.NA↗