On Bragg reflection by helicoidal bianisotropic mediums

Bragg reflection by linear helicoidal bianisotropic mediums (HBMs) is examined. HBMs are periodically nonhomogeneous substances with a preferred axis of rotational nonhomogeneity. Axial excitation of a HBM gives rise to only first-order, but non-axial excitation results in first- as well as higher-order, Bragg reflections, if the chosen HBM is appropriately non-dissipative. Bragg reflections are shown to directly depend on the period of the kernel matrix of a certain matrix differential equation, but only indirectly on the structural period of the HBM.