Scattering of electromagnetic waves by nearly periodic structures

We present a method, based on the coherent potential approximation, for the treatment of disorder in photonic crystals. We apply the method to the stu dy of light absorption by a three-dimensional array of plasma spheres distr ibuted randomly in a host dielectric medium. We find that the effect of dis order on the absorbance of a thick slab of the material consisting of many layers of spheres is much less pronounced than in the corresponding case of a single layer of spheres.