Polarization effects in metallic plates perforated with periodic arrays of subwavelength circular holes

The enhanced transmission phenomenon (ET) discovered by Ebbesen et al has recently been a topic of the intensive research, leading to such a branch of research as fishnet metamaterials. An application of the metamaterials is polarization sensitive devices. Polarization sensitivity for ET frequency selective structures, as for classical ones, is usually associated with the hole shapes being polarization sensitive. This paper discusses a new phenomenon of polarization sensitive extraordinary transmission through a thick screen perforated with polarization independent subwavelength circular holes. The possibility to control the polarization state of the waves transmitted through the screen by manipulation periodical cell dimensions only is shown, while hole shapes are polarization independent. A linear plane wave can be rotated through an arbitrary angle, and converted to a circular or elliptical one, when passing through the screen in the vicinity of Floquet-wave grazing points. Therefore, one can realize a simple and compact polarization device at the expense of reducing bandwidth. The origin of the phenomenon is in a plane wave coupling with different types of symmetry eigenmodes leading to polarization sensitive enhanced transmission. When an incident plane wave couples to orthogonal symmetrical and antisymmetrical eigenmodes with close eigenfrequencies, the screen can behave like a half-wave plate. For the case of several closely spaced eigenmodes jointly contributing to transmitted wave, the effect of enhanced polarization conversion can be observed for the screen to behave like a quarter-wave plate.