ANISOTROPIC EFFECTIVE-MEDIUM THEORIES

The optical properties of anisotropic inhomogeneous media are studied within the framework of the classical 3D effective medium theories of Maxwell Garnett and Bruggeman, and the 2D theory of Yamaguchi et al. The origin of the anisotropy is either the nonspherical shape of the metallic inclusions in the 3D systems, or the distribution of the inclusions (even if spherical) on a substrate in the 2D configuration. In both cases, it leads to an anisotropic effective medium. In this paper, it is shown that this surrounding anisotropic medium induces a fictitious deformation of the inclusions which reduces the anisotropy and shifts the resonance wavelengths toward the sphere plasmon resonance. In the case of the mean field theory of Bruggeman, it also affects the percolation threshold value. Although some of these theories are now quite old, they are still extensively used, especially for the predictions of the absorption of the composite media. Therefore the effect presented here for the first time should be taken into account.