  This study theoretically and experimentally investigates the transmission
properties of a metamaterial slab comprised of two layers of metallic
fish-scale structure arrays and a sandwiched dielectric layer. Calculations
show that the asymmetric transmission can be tuned by varying the slab
thickness, due to evanescent interlayer coupling. The spatial evolution of the
local field inside the structure indicates that the slab functions as a perfect
polarization transformer at certain frequencies in the manner of a waveguide
twist. Measured transmission spectra are in good agreement with calculated
results when material dissipation is considered.
