Effects of negative wave refraction in metallic photonic crystals

The paper considers the interaction of optical radiation with the boundaries of media formed by two-dimensionally periodic systems of well-conducting cylindrical elements of small cross-section – metal photonic crystals. It is shown that at band gap frequencies in the spectrum of the crystal's own electromagnetic states when waves propagate obliquely relative to the elements, such structures can be characterized by hyperbolic isofrequency diagrams in the space of wave vectors. A consequence of this is the possibility of negative refraction effects occurring when waves are incident on the boundary of such an anisotropic hyperbolic medium formed by a two-dimensional crystal with elements of limited length. The problem of incidence of a plane-wave Gaussian optical beam on the surface of a metal photonic crystal is solved using the finite-difference method in the time domain. It has been proven that negative refraction of waves occurs under certain conditions at the boundary of the medium formed by such a crystal.