Clustering effects in composite optical materials

The influence of clustering effects on the susceptibility of composite materials is considered by means of a generalized method of integral equations in the case of a two component medium. For the first time the discrete character of the impurities and of the host medium are both taken into account. We have shown that the clustering of the impurities influences the susceptibility of the composite material in all mixtures except for the case when the host medium is a vacuum. The developed approach may be applied to artificial magnetic materials and to photonic band-gap structures in the long wavelength limit.