Near-zero reflection of all-dielectric structural coloration enabling polarization-sensitive optical encryption with enhanced switchability

Abstract

Structural coloration using metasurfaces has been steadily researched to overcome the limitations of conventional color printing using pigments by improving the resolution, lowering the toxicity, and increasing the durability. Many metasurfaces have been demonstrated for dynamic structural coloration to convert images at the visible spectrum. However, the previous works cannot reach near-zero scattering when colors are turned-off, preventing it from being cryptographic applications. Herein, we propose a completely on/off switchable structural coloration with polarization-sensitive metasurfaces, enabling full-colored images to be displayed and hidden through the control of the polarization of incident light. It is confirmed that the nanostructure exhibits the polarization-dependent magnetic field distributions, and near-zero scattering is realized when the polarization of incident light is perpendicular to the long axis of the nanofins. Also, the metasurfaces are made up of triple-nanofin structures whose lengths affect locations of resonance peaks, resulting in full-color spectrum coverages. With such advantages, a QR code image, a two-color object image, and an overlapped dual-portrait image are obtained with the metasurfaces. Such demonstrations will provide potential applications in the fields of high-security information encryption, security tag, multichannel imaging, and dynamic displays.

Dynamic Structural Colors Based on All‐Dielectric Mie Resonators

“…Later, a complete on/off switch (to realize a full‐colored image under different polarization conditions) was proposed and experimentally demonstrated by Jung et al. [ 150 ]…”

Metasurface-based key for computational imaging encryption

“…Composed of two-dimensional (2D) arrays of nano-/micro-light scatterers (e.g., antennas and resonators), metasurfaces can effectively tailor different DOFs of light with their ultra-thin thicknesses (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), leading to a series of potential applications in optical encryption. By modulating the polarization states and nonlinear responses in multiple channels, metasurface imaging has been used to encode and decode different images (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). By modulating both the spectral and polarization responses, metasurface holography has been successfully applied to hiding different information into different colors and polarization channels (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)…”

“…By modulating the polarization states and nonlinear responses in multiple channels, metasurface imaging has been used to encode and decode different images (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). By modulating both the spectral and polarization responses, metasurface holography has been successfully applied to hiding different information into different colors and polarization channels (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). By controlling the linear polarization states for both the incident light and outgoing light, Malus metasurfaces that operate based on Malus's law have been designed and applied to multi-image encryption and anti-counterfeiting (30)(31)(32)(33)(34).…”

Geometric and physical configurations of meta‐atoms for advanced metasurface holography

“…Metasurfaces are used to modulate the complex wavefront by effectively changing the propagation of light with a designed gradient phase 38 . Taking advantage of these exotic characteristics, various applications of metasurfaces have been reported, including metalenses, 15,39,40 structural coloration, 41–48 beam splitters, 49,50 optical diodes, 51,52 LIDAR, and resolution‐enhancing devices 53,54 …”