Conventional mirrors obey Snell's reflection law: a plane wave is reflected as a plane wave, at the same angle. To engineer spatial distributions of fields reflected from a mirror, one can either shape the reflector (for example, creating a parabolic reflector) or position some phase-correcting elements on top of a mirror surface (for example, designing a reflectarray antenna). Here we show, both theoretically and experimentally, that full-power reflection with general control over reflected wave phase is possible with a single-layer array of deeply sub-wavelength inclusions. These proposed artificial surfaces, metamirrors, provide various functions of shaped or nonuniform reflectors without utilizing any mirror. This can be achieved only if the forward and backward scattering of the inclusions in the array can be engineered independently, and we prove that it is possible using electrically and magnetically polarizable inclusions. The proposed sub-wavelength inclusions possess desired reflecting properties at the operational frequency band, while at other frequencies the array is practically transparent. The metamirror concept leads to a variety of applications over the entire electromagnetic spectrum, such as optically transparent focusing antennas for satellites, multi-frequency reflector antennas for radio astronomy, low-profile conformal antennas for Conventional mirrors, known since the dawn of civilization 1 , obey the simple law of reflection: the reflection angle is equal to the incidence angle. This follows from the fact that the total tangential electric field at the ideal mirror surface is zero, thus, the phase of the electric field in the reflected wave is the opposite to that in the incident wave. If a reflector can be engineered to enable general control over the reflection phase, it is possible to change the direction of the reflected waves at will 2 . Developments in the field of antennas enabled creation of layers with any desired phase of reflection at microwaves. Conceptually, these devices are conventional mirrors, modified by some additional phase-shifting elements positioned close to fully reflecting surfaces. Such artificial layers, in particular conventional reflectarrays 3 and high-impedance surfaces 4 , are realized as arrays of resonant metal patches over a metal ground plane. All the patches of the array usually have identical shape but different dimensions, so that the resonance frequency of an individual patch varies to ensure the desired variations of the reflection phase over the array surface. Controlling the phase variation spanning a 2π range allows one to arbitrarily tune the shape and orientation of the reflected wavefront. Since the conventional reflectarrays incorporate a metal ground plane, the transmission through them is completely blocked and reflection amplitude can be very high if low-loss materials are used. On the other hand, the presence of a metal ground plane forbids transmission at all practically interesting frequencies and limits the application possibilities....

The ideal black body fully absorbs all incident rays, that is, all propagating waves created by arbitrary sources. The known idealized realization of a black body is the perfectly matched layer (PML), widely used in numerical electromagnetics. However, ideal black bodies and PMLs do not interact with evanescent fields existing near any finite-size source, and the energy stored in these fields cannot be harvested. Here we introduce the concept of the ideal conjugate matched layer (CML), which fully absorbs energy of both propagating and evanescent fields of sources acting as an ideal sink for electromagnetic energy. Conjugate matched absorbers have exciting application potentials, as resonant attractors of electromagnetic energy into the absorber volume. We derive the conditions on the constitutive parameters of media which can serve as CML materials, numerically study the performance of planar and cylindrical CML and discuss possible realizations of such materials as metal-dielectric composites.

No abstract

No abstract

This paper presents and discusses the conditions for zero electromagnetic scattering by electrically small particles. We consider the most general bi-anisotropic particles, characterized by four dyadic polarizabilities and study the case of uniaxially symmetric objects. Conditions for zero backward and forward scattering are found for a general uniaxial bi-anisotropic particle and specialized for all fundamental classes of bi-anisotropic particles: omega, "moving", chiral, and Tellegen particles. Possibility for zero total scattering is also discussed for aforementioned cases. The scattering pattern and polarization of the scattered wave are also determined for each particle class. In particular, we analyze the interplay between different scattering mechanisms and show that in some cases it is possible to compensate scattering from a polarizable particle by appropriate magneto-electric coupling. Examples of particles providing zero backscattering and zero forward scattering are presented and studied numerically. Index Terms-Bi-anisotropic media; scattering J. Vehmas, Y. Ra'di and S. A. Tretyakov are with the

No abstract

No abstract

In this paper we introduce the concept of transmission lines with inherent bianisotropy and establish an analogy between these lines and volumetric bi-anisotropic materials. In particular, we find under what conditions a periodically loaded transmission line can be treated as an effective omega medium. Two example circuits are introduced and analyzed. The results have two-fold implications: opening a route to emulate electromagnetic properties of bi-anisotropic omega media using transmissionline meshes and understanding and improving effective medium models of composite materials with the use of effective circuit models of unit cells.