Phys. Rev. B, 60 1555 (1999)

It is known that photonic Bloch states can become strongly localized near the band edges in a disordered photonic crystal. We show that Bloch states are disrupted and another localization regime establishes when local fluctuations of the band-edge frequency caused by randomization of refractive index profile becomes as large as the band-gap width. Transmission experiments performed on opal photonic crystal have shown the exponential decay of light throughout the gap region, which is ascribed to building up of the second regime of light localization.