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:

Abstract-An analytical theory of electromagnetic waves in artificial media formed by a rectangular lattice of thin ideally conducting cylinders using the local field approach is developed. As a result, the transcendental dispersion equation is obtained in closed form and solved numerically. Typical dispersion curves are calculated. Using these results, the reflection problem from an interface between a half space of wire medium and free space is solved for plane-wave excitation. In the low-frequency approximation a simple analytical formula for the frequency dependent effective dielectric permittivity is established.

A transversal mode with zero group velocity and nonzero phase velocity that can exist in chains of silver nanospheres in the optical frequency range is theoretically studied. It is shown that the external source radiating a narrow-band nonmonochromatic signal can excite in the chain a mixture of standing and slowly traveling waves. The standing-wave component (named the resonator mode) is strongly dominating. The physical reason for such a regime is a sign-varying distribution of power flux over the cross section of the chain. A possible application of the resonator mode for evanescent-wave enhancement and for subwavelength imaging in the visible is discussed.

Experimental evidence of the nonreciprocal Tellegen magnetoelectric effect is presented. The measured particle consists of a small ferrite sphere and a small piece of a thin metal wire glued to the sphere. The whole system is magnetized by a permanent magnet. The Tellegen effect was observed experimentally when this particle was positioned in a rectangular waveguide and excited by a small wire loop. This result experimentally confirms by a direct observation in the microwave range the known theoretical conclusions and experimental evidences at low frequencies regarding mistakes in some theoretical papers that claimed nonexistence of the Tellegen effect.

Near-field enhancement and sub-wavelength imaging properties of a system comprising a coupled pair of two-dimensional arrays of resonant nanospheres are studied. The concept of using two coupled material sheets possessing surface mode resonances for evanescent field enhancement is already well established in the microwave region. This paper shows that the same principles can be applied also in the optical region, where the performance of the resonant sheets can be realized with the use of metallic nanoparticles. In this paper we present design of such structures and study the electric field distributions in the image plane of such superlens.

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Electromagnetic waves in an artificial medium formed by two mutually orthogonal lattices of thin ideally conducting straight wires (referred to as a two-dimensional wire medium) are considered. An effective medium approach and a full-wave method based on the dyadic Green's function and the method of moments are developed. Effects of spatial dispersion, such as the appearance of anisotropy in a square lattice and an additional extraordinary wave, as in crystal optics, are demonstrated. Evanescent waves with complex propagation constants are found. The case when both forward and backward extraordinary waves with respect to an interface exist simultaneously is observed and discussed. The effect of birefringence, so that one extraordinary wave has the wave vector making a positive angle to the interface and the other has the wave vector making a negative angle to the interface, is illustrated.