  It has recently been shown that the transmission of electromagnetic fields
through sub-wavelength slits (parallel to the electric field direction) in a
thin metallic screen can be greatly enhanced by covering one side of the screen
with a metallic cut-wire array laid on a dielectric layer. In this Letter, we
show that a richer phenomenology (which involves both electric- and
magnetic-type resonances) can be attained by pairing a second cut-wire array at
the other side of the screen. Via a full-wave comprehensive parametric study,
we illustrate the underlying mechanisms and explore the additional degrees of
freedom endowed, as well as their possible implications in the engineering of
enhanced transmission phenomena.
