Exceptional Guided Waves

The planar interface of two dissimilar partnering mediums, at least one of which is anisotropic, can guide an exceptional surface wave that propagates in an isolated direction. In order for this to be achieved, the constitutive parameters of the partnering mediums must satisfy certain constraints. Exceptional surface waves have localization characteristics that distinguish them from unexceptional surface waves: the decay of fields of an exceptional surface wave in an anisotropic partnering medium exhibits a combined linear-exponential dependency on distance from the interface, whereas the decay is purely exponential for an unexceptional surface wave. The notion of exceptional surface waves can be extended to compound waves that are guided by a pair of parallel planar interfaces.