Gyrotropic Bandgaps, Degeneracy Lifting and Selective Suppression of   Bloch States in Photonic Systems
  Birefringent magnetophotonic crystals are found to exhibit degeneracy breaking for asymmetric contradirectional coupling in planar waveguides. Fundamental to high-order local normal mode coupling leads to partially overlapping gyrotropic bandgaps inside the Brillouin zone and partial suppression of Bloch mode propagation. A large magneto-optically active reorientation in polarization state is found for allowed Bloch modes at bandgap edges. 
Miguel Levy, Amir A. Jalali, Z. Zhou and N. Dissanayake