Backward waves and negative refraction in photonic (electromagnetic) crystals

A detailed review on excitation of backward waves and negative refraction in photonic (electromagnetic) crystals is presented. Classification into forward and backward waves in linear media is considered in relation to the phenomenon of refraction at the isotropic dielectric-crystalline medium interface. The role of the interface orientation with respect to the intrinsic geometry of the medium is clarified. The feasibility of negative refraction in the absence of a backward wave is illustrated by simple examples; an example of negative refraction and backward wave excitation in a nonmagnetic crystal are given.