Polarizing and angle-sensitive color filter in transmittance for security feature applications

Subwavelength gratings comprising a stack of two thin metallic wire gratings embedded in a dielectric exhibit distinctive color properties in transmittance. Its angle-dependent coloring can be easily noticed by human observers in ambient light. Moreover, it has pronounced polarizing properties in the visible wavelength range. The optical properties of these gratings have been numerically studied. The results have been confirmed by manufactured samples replicated by a simple nanoimprint process on plastic foils. The manufacturing process is predestined for industrial mass production. Applications as authentication devices are given.