Nonreciprocal photonic band structure of low-symmetry magnetic photonic crystals

We propose multicomponent magnetic photonic crystals as a basis component for nonreciprocal optical elements. It is shown that introduction of three or more components may provide violation of mirror reflection symmetry, which is a necessary condition for obtaining nonreciprocity in the dispersion of the structure's eigenmodes. Numerical simulations confirm that nonreciprocity indeed develops in the form of nonreciprocal photonic band structure of three-component low-symmetry photonic crystal. We find that symmetry constraints produce fine structure in the nonreciprocity at high-symmetry points of the Brillouin zone.