Wavelength dispersion of 1D photonic crystals

Periodic multilayer film (the simplest 1D photonic crystal) is commonly utilized as wavelength splitting filters, because the multilayer structure has PBG(photonic band gaps) along the direction of lamination. Although the structure has no PBG along spreading directions, plural photonic bands make unique propagations of electromagnetic waves. A very large dispersion of refracted rays from the surfaces were experimentally observed and theoretically analyzed.