Existence of a photonic band gap and underlying physical processes

Mechanisms of the overlapping of gaps due to a refractive index difference minimum and Anderson localization for photonic band gap (PBG) have been use d and they give a refractive index contrast difference of less than two per cent for X-, L-, and W-points of the Brillouin zone for the pseudogap. Anot her physical process for the existence of PBG is the use of scattering stre ngth (epsilon (r) greater than or equal to 1) for fee lattice structure. We have found refractive index contrast in the range 2.41-14.21 for the exist ence of the complete photonic band gap for bound photons (epsilon (r) great er than or equal to 1). The lowest limit to yield a gap is 2.41 for valence photons (epsilon (r) = 1) at volume filling fraction 85.5% for spherical a ir atoms and at 14.5% for dielectric spheres. This work is reported for the first time and it is useful for maintaining connectivity and for easier fa brication of photonic crystals.