Kerker-Conditioned Dynamic Cryptographic Nanoprints

Abstract

High-quality and tunable structural color printing with feasible fabrication is a key goal in recent decades, holding the possibility for full-color microdisplay and impeccable cryptographic nanoprints. Plasmonic approach suffers from the inevitable material absorption restricting the color spectrum with suppressed lightness. Recent progress in dielectric nanophotonics offers low-loss solution for color rendering, but dynamic functionality is still in infancy of changing colors with unchanged portraits, where more sophisticated physical mechanisms are in demand. Here, a strategy using full Kerker's conditions is reported to design low-loss silicon metasurfaces which can generate broad spectrum of colors beyond the standard Red Green Blue (sRGB) gamut. The combination of the two Kerker's conditions enables dynamic and bright color palettes and full-color microdisplay. Meanwhile, the asymmetric unit-cell can guarantee polarization-angle-controlled reflective response with greatly sharpened spectra by complete control of the Kerker's effects. As a proof-of-concept, polarization-encrypted images are demonstrated where completely distinguished pieces of information can be decoded exclusively only in predetermined polarization angle. They serve as highly-secured cryptographic nanoprints that can be integrated with conventional smartphone technology. The complementary-metal-oxide-semiconductor (CMOS)-compatible metasurfaces can provide a new roadmap of anti-counterfeiting tagging, advanced optical data storage, and tunable high-contrast microprinting for real-life applications.