Semi-permeable resonant aluminum gratings for structural coloration in transmission

The novel type of diffraction gratings consists of a semi-permeable corrugated aluminum film with periods supporting first-order diffraction in the visible wavelength range. These gratings exhibit coloring of the transmitted zeroth order due to excitation of surface plasmons. The hue depends on the angle of incidence and may be adjusted by varying the grating period. Manufactured samples with motifs containing grating arrays of different periods demonstrate a wide range of achievable colors. The fabrication process is suited for scale-up to large area production, since the replication on plastic foils can be implemented as a cost-effective roll-to-roll process. These gratings have practical applications as security features, since they are fully compatible to widely used rainbow holograms.