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This paper describes digital printing of optical metasurfaces for ink-free colour decoration and flat optics, by holographic laser post-writing on nano-textured, metal-coated optical metasurfaces.
Our optical metasurfaces are based on the concepts of both localized surface plasmon resonances (LSPR) and high-index dielectrics compatible with technologies for high volume manufactured plastic products. The optical metasurfaces are formed by nanoimprinting a surface texture comprising nanoscale cylinders. By subsequent deposition of a thin film of metal or high index dielectric, isolated nano-discs are formed on top of the cylinders, while a continuous film is formed on the substrate surface in between the cylinders. The nano-scale disks and corresponding holes in the continuous film form optical resonators. The master-original for the square-centimeter nano-texture is realized by means fast e-beam writing. The nanotextured plasmonic metasurface may be covered with a transparent protective coating, which can withstand the daily life handling.
Laser post-writing can modify disks and holes, and hence the optical resonances. Laser pulses induce transient local heat generation that leads to melting and reshaping of the imprinted nanostructures. This enables flexible definition and alignment of optical components on high volume manufactured plastic products. Our approach offers a printing speed of 1 ns per pixel (in raster scan), resolution up to 127,000 dots per inch (DPI) and power consumption down to 0.3 nJ per pixel.
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