Nonreciprocal composite with the material relations of the transparent absorbing boundary

Abstract

The recently introduced transparent absorbing boundary for the termination of computational domains in finite methods can be described by the constitutive relations of the same type as that of moving media. In this paper, it is shown that the same constitutive relations can be, in principle, realized in certain nonreciprocal magnetoelectric composites. Eigensolutions and the frequency behavior of the propagation factors in these artificial media are discussed. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 365–368, 1998.

Transmission lines emulating moving media

“…Therefore, our model when considering a finite slab corresponds, in fact, to a medium which is moving, but its boundaries remain stationary, similar to the movement of a conveyor belt (the other side of which is hidden from view). Obviously, this is also the case for any artificial realization of moving media lacking nonlinear elements or materials (e.g., [3,5,8]). …”

“…The propagation constants β ± for axially (along z) propagating plane waves in moving media can be easily derived, combining the Maxwell equations with the material parameters (e.g., [2,5]) It is given by…”

“…In that case, the refractive index of the host line limited the dispersion so that we always had + − > n V n V , 1 leading to the limits β > + k 0 and β < − − k 0 , according to (5). It is well known that an ideal left-handed transmission line (characterized by an equivalent circuit consisting of a series capacitor and a shunt inductor) has a negative refractive index [13].…”

“…Suggested realizations of an artificial moving medium based on embedding electrically small inclusions (consisting of a swastika-shaped metal element on top of a small magnetized ferrite sphere into a dielectric [3,5]) suffer from parasitic chirality of the inclusions. Also, the suggested inclusions are resonant structures leading to a highly dispersive response.…”

“…These material relations with anti-symmetric coupling dyadics correspond to a nonreciprocal class of bi-anisotropic media called, by analogy, moving media [3,4], although the medium does not move, and the coupling is provided (due to its microstructure containing some nonreciprocal elements). It appears that materials obeying (1) and (2) have not been found among natural materials, but there have been conceptual suggestions on how such materials can be possibly realized using composites containing magnetized ferrite and metal inclusions [3,5]. In the artificial-medium scenario, the values of the velocity parameter in the constitutive relations are not restricted to real values smaller than the speed of light, so this opens exciting opportunities to realize structures that emulate (fictitious) electromagnetic phenomena for media moving with superluminal or even complex-valued velocities.…”