We study a system composed of two thin crossed lamellar gratings, with
lamellae composed of a Drude metal. We show that such a system can yi
eld striking behavior for wavelengths of electromagnetic radiation muc
h longer than the grating period, with reflectance, transmittance, and
absorptance being independent of wavelength. We thus present periodic
models that can duplicate the behavior of thin critical metallic film
s while having a much simpler and more practical geometry than they.