arXiv subjects

Igor Nefedov

Publications and source records attributed to Igor Nefedov.

6 recordsLinked to original sources

arXiv2014

Super-Planckian far-zone thermal emission from asymmetric hyperbolic metamaterials

In this paper we demonstrate that asymmetric hyperbolic metamaterials (AHM) can produce strongly directive thermal emission in far-field zone, which exceeds Planck's limit. Asymmetry is inherent in an uniaxial medium, whose optical axes are tilted with respect to medium interfaces and appears as a difference in properties of waves, propagating upward and downward with respect to the interface. It's known that a high density of states (DOS) for certain photons takes place in usual hyperbolic metamaterials, but emission of them into a smaller number in vacuum is preserved by the total internal reflection. However, the use of AHM enhance the efficiency of coupling of the waves in AHM with the waves in free space that results in Super-Planckian far-field thermal emission in certain directions. Different plasmonic metamaterials can be used for realization of AHM. As example, thermal emission from AHM, based on graphene multilayer, is discussed.

physics.optics↗

arXiv2011

Giant radiation heat transfer through the micron gaps

Near-field heat transfer between two closely spaced radiating media can exceed in orders radiation through the interface of a single black body. This effect is caused by exponentially decaying (evanescent) waves which form the photon tunnel between two transparent boundaries. However, in the mid-infrared range it holds when the gap between two media is as small as few tens of nanometers. We propose a new paradigm of the radiation heat transfer which makes possible the strong photon tunneling for micron thick gaps. For it the air gap between two media should be modified, so that evanescent waves are transformed inside it into propagating ones. This modification is achievable using a metamaterial so that the direct thermal conductance through the metamaterial is practically absent and the photovoltaic conversion of the transferred heat is not altered by the metamaterial.

physics.optics↗

arXiv2011

An ultra-broadband electromagnetically indefinite medium formed by aligned carbon nanotubes

Anisotropic materials with different signs of components of the permittivity tensor are called indefinite materials. Known realizations of indefinite media suffer of high absorption losses. We show that periodic arrays of parallel carbon nanotubes (CNTs) can behave as a low-loss indefinite medium in the infrared range. We show that a finite-thickness slab of CNTs supports the propagation of backward waves with small attenuation in an ultra-broad frequency band. In prospective, CNT arrays can be used for subwavelength focusing and detection, enhancing the radiation efficiency of small sources.

physics.optics↗

arXiv2008

Generalized field-transforming metamaterials

In this paper we introduce a generalized concept of field-transforming metamaterials, which perform field transformations defined as linear relations between the original and transformed fields. These artificial media change the fields in a prescribed fashion in the volume occupied by the medium. We show what electromagnetic properties of transforming medium are required. The coefficients of these linear functions can be arbitrary scalar functions of position and frequency, which makes the approach quite general and opens a possibility to realize various unusual devices.

physics.optics↗

arXiv2006

Vector circuit theory for spatially dispersive uniaxial magneto-dielectric slabs

We present a general dyadic vector circuit formalism, applicable for uniaxial magneto-dielectric slabs, with strong spatial dispersion explicitly taken into account. This formalism extends the vector circuit theory, previously introduced only for isotropic and chiral slabs. Here we assume that the problem geometry imposes strong spatial dispersion only in the plane, parallel to the slab interfaces. The difference arising from taking into account spatial dispersion along the normal to the interface is briefly discussed. We derive general dyadic impedance and admittance matrices, and calculate corresponding transmission and reflection coefficients for arbitrary plane wave incidence. As a practical example, we consider a metamaterial slab built of conducting wires and split-ring resonators, and show that neglecting spatial dispersion and uniaxial nature in this structure leads to dramatic errors in calculation of transmission characteristics.

physics.class-ph↗

arXiv2002

Waves and energy in chiral nihility

A model for a chiral material in which both the permittivity and permeability are equal to zero is discussed. Such a material is referred by us as a ``chiral nihility". It is shown that this exotic material can be realized as a mixture of small helical inclusions. Wave solutions and energy in such a medium are analyzed. It is shown that an extraordinary wave in chiral nihility is a backward wave. Wave reflection and refraction on a chiral nihility interface is also considered. It is shown that a linearly polarized wave normally incident onto this interface produces the wave of "standing phase" and the same wave in the case of oblique incidence causes two refracted waves, one of them with an anomalous refraction.

cond-mat↗