BW media—media with negative parameters, capable of supporting backward waves

TLDR

The phenomenon of backward waves has attracted recent interest, with man‑made composite media termed “media with negative refraction factor” or “left‑handed materials” being effective in a microwave band, yet these names are not well founded, prompting the suggestion of the term “backward‑wave medium” (BW medium). This paper reviews isotropic and uniaxially anisotropic media capable of supporting backward waves, discusses the significance of Zenneck waves and guided modes in a cylindrical BW guide, and extends the BW property to uniaxial anisotropic media by studying various parameter combinations. The authors analyze BW media by reviewing their isotropic and anisotropic forms, examining Zenneck wave behavior and guided modes in cylindrical guides, and exploring the occurrence of BW characteristics across different uniaxial parameter sets. They show that at a regular–BW interface Snell’s law does not imply a negative refraction factor, yet the transmitted plane wave is a backward wave with opposing Poynting and wave vectors, and that a lateral backward wave can arise when one of the four parameters of a uniaxial medium is negative. © 2001 John Wiley & Sons, Inc., Microwave Opt Technol Lett 31:.

Abstract

Abstract Both isotropic and uniaxially anisotropic media capable of supporting backward waves are reviewed. Such an effect recently has been of great interest, and certain man‐made composite media have been introduced under the names “media with negative refraction factor” or “left‐handed materials,” effective in a certain band of microwaves. Neither of these names appears to be well founded, and “backward‐wave medium” (or BW medium) is suggested instead. It is shown that, at an interface of a regular and a BW medium, Snell's law does not imply a negative refraction factor. However, the refraction is anomalous in the sense that the transmitted plane wave is a backward wave with a Poynting vector and a wave vector pointing in opposite lateral directions. The significance of the Zenneck wave and guided modes in a cylindrical guide made of BW medium is discussed. Finally, the BW property is extended to uniaxially anisotropic media, and its occurrence is studied for different value combinations of its medium parameters. It is shown that a lateral backward wave can arise when a plane wave is transmitted through an interface when one of the four parameters of the uniaxial medium is negative. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 129–133, 2001.