Studies of polaritonic gaps in photonic crystals.

In a photonic band structure two kinds of gaps with different origins can be observed. Photonic gaps are determined by the symmetry of the photonic crystal, the lattice constant, and the contrast of the dielectric functions for the two components. Polaritonic gaps originate from the bulk optical properties of one of the components. Excitation of ionic components in the lattice results in a photon energy interval in which the dielectric function is negative. Here we investigate the interaction between photonic gaps and polaritonic gaps in one-dimensional and two-dimensional photonic structures. In particular, we show that by such interactions the polaritonic gap can be made wider and stronger, be left unchanged, or be made to vanish.