Functional optical metamaterials employing spatial dispersion and absorption

Functional optical metamaterials usually consist of absorbing, anisotropic and often non-centrosymmetric structures of a size that is only a few times smaller than the wavelength of visible light. If the structures would be substantially smaller, excitation of higher-order electromagnetic multipoles in them, including magnetic dipoles, would be inefficient. As a result, the material would act as an ordinary electric-dipole material. The required non-negligible size of metamolecules, however, makes the material spatially dispersive, so that its optical characteristics depend on light propagation direction. This phenomenon significantly complicates the description of metamaterials in terms of conventional electric permittivity and magnetic permeability tensors. In this work, we present a simple semianalytical method to describe such spatially dispersive metamaterials, which are also allowed to be optically anisotropic and non-centrosymmetric. Applying the method, we show that a strong spatial dispersion, combined with absorption and optical anisotropy, can be used to efficiently control propagational characteristics of optical beams.