Dispersion curve calculations for photonic opals and inverse opals have been performed with the aim of study the influence of the dielectric contrast and of the size of the spheres on the widths of the photonic band gaps. Disorder effects in this kind of system have been briefly discussed. Moreover, structural-defects and punctual-defects, which generate photonic states inside the photonic band gap have been studied by using Large Unit Cells approach.
The optical response of a thick slab of a two-dimensional photonic crystal, obtained by taking a rectangular dielectric grating as the elementary building block, is computed and compared with the dispersion curve of the bulk. The role of the bulk and the surface waves of the system on the optical transmittivity is discussed. The “mirror effect”, computed by two of the present authors in self-sustained rectangular dielectric gratings, due to the interplay among traveling, evanescent and guided waves, is recovered and it seems to endure also in the semi-infinite photonic crystal.