I. Introduction
THERE HAS been great interest in the last few years in trying to understand the properties of structures configured for making focusing devices capable of having radically new properties based on the concepts coming from the use of what has been variously referred to in the literature as negative media, left-handed media, double-negative media, or backward-wave media [1]–[12]. There are many unusual properties of such media and, although in the physics and electronics literature many fascinating issues have been explored, we will not address what has held the attention of most researchers, which are the properties leading to convergent focusing behavior [1], [3] when ordinary media would lead to divergent rays and the attendant perfect focusing consequences. All that will be stated is that in light of multidimensional aspects of real lensing systems, and imperfect media, including finite dispersion and finite loss, the sought-after effect may turn out to be not quite what was expected [5], [11], although still tremendously interesting nevertheless.