Nonreciprocal Effects in Magnetic Photonic Crystals

Abstract

Magnetic photonic crystals are periodic arrays of lossless materials, at least one of which being magnetically polarized. Magnetization, either spontaneous or induced, is associated with nonreciprocal effects, such as Faraday rotation. In addition, magnetic photonic crystals of certain configuration can also display strong spectral asymmetry, implying that electromagnetic waves propagate in one direction much faster or slower than in the opposite direction. This essentially nonreciprocal phenomenon can result in electromagnetic unidirectionality. A unidirectional medium, being perfectly transmissive for electromagnetic waves of certain frequency, freezes the radiation of the same frequency propagating in the opposite direction. The frozen mode has zero group velocity and drastically enhanced amplitude. Here we study the nonreciprocal phenomena in magnetic photonic crystals and establish physical conditions under which such phenomena can be significant. Particular attention is given to the relation between structural geometry of the periodic array, the electromagnetic dispersion relation, and the character of the frozen mode regime. We also discuss the peculiarities of transmission band gap resonance in nonreciprocal periodic layered structures. ASYMMETRY OF THE BLOCH DISPERSION RELATION IN MAGNETIC PHOTONIC CRYSTALS