Constantinos A. Valagiannopoulos

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The interaction between a metamaterial cylindrical structure and an incident plane wave is investigated. The structure is comprised of two cylinders, one embedded into the other, whose effective characteristics vary with the operating frequency following similar laws. Such a model can be used to describe periodic structures, constituting metamaterials, with(More)
Finite-thickness slabs of hyperbolic media with tilted optical axes exhibit asymmetry properties for waves propagating upward and downward with respect to slab interfaces. Under certain conditions, asymmetric hyperbolic media acquire extreme permittivity parameters and the difference between upward and downward propagating waves becomes very large.(More)
The permittivity tensor of an anisotropic material can be predicted with use of the presented technique. A slab of this substance possessing infinitesimal thickness is illuminated by a normally incident plane wave and rigorous expressions for the transmission coefficients are obtained. The derived formulas are linearly expanded with respect to the small(More)
A grounded dielectric film-slab is externally excited by a normally-incident Gaussian beam. A single superstrate dielectric layer, with suitably selected parameters, is placed on top of the film-slab in order to increase the power concentration inside the slab. A basic quantity of interest, called “enhancement factor” is defined, which(More)
One of the main problems when trying to detect the position and other characteristics of a small inclusion into lossy Earth via external measurements is the object’s poor scattering response due to attenuation. Hence, increasing the scattered power generated by the inclusion when using not an active but a passive material is of great interest. To this(More)
Marios Mattheakis, 2, ∗ Constantinos A. Valagiannopoulos, † and Efthimios Kaxiras 4 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA Crete Center for Quantum Complexity and Nanotechnology, Department of Physics, University of Crete, Heraklion 71003, Greece Department of Physics, Nazarbayev University,(More)
Francesco Monticone, Constantinos A. Valagiannopoulos, and Andrea Alù Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, USA Department of Physics, School of Science and Technology, Nazarbayev University, KZ-010000 Astana, Kazakhstan Center for Nanophotonics, FOM Institute for Atomic and Molecular(More)
Several wave scattering phenomena in optics are modeled by the method of fictitious sources (MFS). Despite its interesting features, the effectiveness of the MFS and its applicability are restricted by open issues, including the placement of the fictitious sources (FS) and the fields' convergence. Concerning these issues, we investigate here the MFS(More)
It has been recently shown that in the case of scattering by a perfect electric conductor, it is possible to have a convergent Method of Auxiliary Sources (MAS) field due to divergent MAS currents. These conclusions are extended in the present paper for the case of the implementation of MAS to dielectric scattering problems. The main differences are pointed(More)
Aberration-Free Imaging Based on Parity-Time Symmetric Nonlocal Metasurfaces Francesco Monticone1*, Constantinos A. Valagiannopoulos1,2*, and Andrea Alù1,3+ 1Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712, USA 2Department of Radio Science and Engineering, Aalto University, Finland 3FOM Institute AMOLF,(More)