BW Media: Media with Negative Parameters, Capable of Supporting Backward Waves.

摘要

Both isotropic and uniaxially anisotropic media capable of supporting backward waves are reviewed. Such an effect has been recently under 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 Poynting vector and wave vector pointing to opposite lateral directions. The significance to 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.