Polarization degeneracy at Bragg reflectance in magnetized photonic crystals

A study is presented of the band structure in one-dimensional photonic crystals with anisotropic and gyrotropic layers. It is predicted that magnetization of the structure in a direction normal to the plane of the layers causes the formation of an additional band gap of a new type. The phenomenon is caused by the Bragg resonance between harmonics of different polarization and stems from the hybridization of these harmonics. Though the application of a magnetic field generally results in degeneracy lifting, in anisotropic magnetophotonic crystals a magnetic field may actually induce polarization-degenerate Bragg reflections. Moreover, while in a nonmagnetized photonic crystal, the Bloch waves of different polarization may have noncoincident band edges, the band gaps predicted herewith are shared by the Bloch waves of any polarization. This allows the design of polarization- independent optical tuning devices. Thus the formation of these band gaps enables the magnetic control of arbitrarily polarized light. © 2009 The American Physical Society