I. Introduction
In Certain linear and deterministic electromagnetic (EM) propagation/scattering scenarios, ray trajectories may become exponentially sensitive to small changes in the initial conditions, thereby exhibiting long-range-unpredictable dynamics. Remarkably, while this could intuitively be expected in very complex and cluttered propagation scenarios, it can also be observed in deceptively simple (but coordinate-nonseparable) structures that give rise to multiple reflections, focusing, and defocusing, such as “billiard-shaped” enclosures [1], [2], -disk “pinballs” [3], [4], or appropriately configured inhomogeneous refractive media with ray-trapping properties [5]. Such pathological behavior can be properly characterized within the framework of deterministic chaos theory [6], and is accordingly referred to as “ray chaos.”