Extraordinary transmission through dielectric-loaded metascreens

A conducting metal plate with periodically spaced electrically small apertures forms what has been called a metascreen—a particular example of a metasurface. Under ordinary conditions, such a metascreen merely functions as a bandstop filter for waves of sufficiently low frequency. It has been found that at optical frequencies where a metal has electromagnetic properties vastly different from those of a perfect conductor and a thickness different from zero, abnormally large transmission can occur when the size of the apertures is significantly smaller than a wavelength (T. W. Ebbesen et al., Nature, 391, 667–669, 1998). In this case, the mechanism responsible for this “extraordinary transmission” was found to be the coupling of the electromagnetic wave with surface plasmons on the nonideal metal.