From unexceptional to doubly exceptional surface waves

TL;DR

This paper investigates special surface waves called exceptional and doubly exceptional waves that propagate in specific directions with unique decay properties at the interface of anisotropic and isotropic media.

Contribution

It introduces the concept of doubly exceptional surface waves, expanding the understanding of wave localization in anisotropic interfaces.

Findings

Exceptional surface waves propagate in isolated directions with linear-exponential decay.

Doubly exceptional surface waves exist when both media are anisotropic, with decay governed by combined linear-exponential functions.

The study characterizes conditions for the existence of these unique surface waves.

Abstract

An exceptional surface wave can propagate in an isolated direction, when guided by the planar interface of two homogeneous dielectric partnering mediums of which at least one is anisotropic, provided that the constitutive parameters of the partnering mediums satisfy certain constraints. Exceptional surface waves are distinguished from unexceptional surface waves by their localization characteristics: the fields of an exceptional surface wave in the anisotropic partnering medium decay as a combined linear-exponential function of distance from the interface, whereas the decay is purely exponential for an unexceptional surface wave. If both partnering mediums are anisotropic then a doubly exceptional surface wave can exist for an isolated propagation direction. The decay of this wave in both partnering mediums is governed by a combined linear-exponential function of distance from the interface.