Laser Writing of Bright Colors on Near-Percolation Plasmonic Reflector Arrays.

Abstract

Coloration by surface nanostructuring has attracted a great deal of attention by the virtue of making use of environment-friendly recyclable materials and generating nonbleaching colors. Recently, it was found possible to delegate the task of color printing to laser postprocessing that modifies carefully designed and fabricated nanostructures. Here we take the next crucial step in the development of structural color printing by dispensing with preformed nanostructures and using instead near-percolation metal films atop dielectric-metal sandwiches, that is, near-percolation plasmonic reflector arrays. Scanning rapidly (∼20 μm/s) across 4 nm-thin island-like gold films supported by 30 nm-thin silica layers atop 100 nm-thick gold layers with a strongly focused Ti-sapphire laser beam, while adjusting the average laser power from 1 to 10 mW, we produce bright colors varying from green to red by laser-heating-induced merging and reshaping of gold islands. Selection of strongly heated islands and their reshaping, both originating from excitation of plasmonic resonances, are strongly influenced by the polarization direction of laser illumination, so that the colors produced are well pronounced only when viewed with the same polarization. Conversely, the laser color writing with circular polarizations results in bright polarization-independent color images. The fabrication procedure for near-percolation reflector arrays is exceedingly simple and scalable to mass production, while the laser-induced modification occurs inherently with the subwavelength resolution. This combination of features makes the approach developed for laser color writing readily amenable for practical implementation and use in diverse applications ranging from nanoscale patterning for security marking to large-scale color printing for decoration.