In differential-form representation, the Maxwell equations are represented by simple differential relations between the electromagnetic two-forms and source three-forms while the electromagnetic medium is defined through a constitutive relation between the twoforms. The simplest of such relations expresses the electromagnetic two-forms as scalar multiples of one another. Because of its strange properties, the corresponding medium has been considered as nonphysical. In this study such a medium is interpreted in terms of the classical Gibbsian vectors as a bi-isotropic medium with infinite values for its four medium parameters. It is shown that the medium is a generalization of both PEC (perfect electric conductor) and PMC (perfect magnetic conductor) media, with similar properties. This is why the medium is labeled as PEMC (perfect electromagnetic conductor). Defining a certain class of duality transformations, PEMC medium can be transformed to PEC or PMC media. As an application, plane-wave reflection from a planar interface of air and PEMC medium is studied. It is shown that, in general, the reflected wave has a cross-polarized component, which is a manifestly nonreciprocal effect.
Geometrical optics approximation for waves in inhomogeneous chiral media is introduced based on the concept of normalized wave fields, which are certain complex combinations of the electric and magnetic fields, uncoupled for sufficiently slowly varying meia. For small values of the chirality paraneter, the geometrical optics rays can be calculated as for achiral media and the main effect of the chirality is rotation of polarization along the ray. Thus, adding chirality to inhomogeneous lens antennas, their polarization properties can be improved. As an example, it is demonstrated how the inherent cross polarization of the Maxwell fish-eye lens is compensated through a suitable chirality distribution.
THEORYElectromagnetic fields in chiral media satisfy constitutive equations which may be written in the following form:D-=E -jvJicH, B = jny/jhE + sH,(1) and the source-free Maxwell equations V x E =-jkyH + k0nE, V x H=-%E + k0H.(2) 17 It is assumed that all medium parameters may be dependent on the position vector r: k = ka/4 = k0n(r), 1 = cr)' K = K(r).(Note that the definition of the chirality parameter denoted here by r. is somewhat different from those given in other literature, e.g., [1], [2]. The connection to other representations, is, however, quite straightforward. The medium parameters c, i, K form a mathematical representation of the chiral medium whatever its mricroscopic physical structure. It should be noted that in making artificial chiral media, e.g., through adding metal helices in a base material, all three parameters are changed, in general. Wave fields Let us consider the solution in terms of normalized wave field vectors F± and F defined in terms of the (unnormalized) wave field vectors Et [3] -[5] F± = I E± -EE± =1 E j7H]Conversely, the electric and magnetic fields can be obtained from the wave -fields as follows:
A set of boundary conditions requiring vanishing of the normal components of the D and B vectors at the boundary surface is introduced and labeled as that of DB boundary. Basic properties of the DB boundary are studied in this paper. Reflection of an arbitrary plane wave, incident with a complex propagation vector, is analyzed for the planar DB boundary. It is shown that waves polarized transverse electric ͑TE͒ and transverse magnetic ͑TM͒ with respect to the normal of the boundary are reflected as from respective perfect electric conductor and perfect magnetic conductor planes. The basic problem of current source above the planar DB boundary is solved by applying TE and TM decomposition for the source. Realization of the DB boundary in terms of an interface of uniaxially anisotropic metamaterial half-space with zero axial medium parameters is considered. It is also shown that such a medium with small axial parameters acts as a spatial filter for waves incident at the interface which could be used for narrowing the beam of a directive antenna. Application of DB boundary as an isotropic soft surface with low interaction between antenna apertures also appears possible.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.