Laser-Splashed Three-Dimensional Plasmonic Nanovolcanoes for Steganography in Angular Anisotropy

Abstract

Planar optics constructed from subwavelength artificial atoms have been suggested as a route to the physical realization of steganography with controlled intrinsic redundancy at single-pixel levels. Unfortunately, two-dimensional geometries with uniform flat profiles offer limited structural redundancy and make it difficult to create advanced crypto-information in multiplexed physical divisions. Here, we reveal that splashing three-dimensional (3D) plasmonic nanovolcanoes could allow for a steganographic strategy in angular anisotropy, with high resolution, full coloration, and transient control of structural profiles. Highly reproducible 3D morphologies of volcanic nanosplashes are demonstrated by creating a standardized recipe of laser parameters. Such single nanovolcanoes can be well controlled individually at different splashing stages and thus provide a lithography-free fashion to access various spectral responses of angularly coordinated transverse and vertical modes, leading to the full-range coloration. This chip-scale demonstration of steganographic color images in angular anisotropy unfolds a long-ignored scheme for structured metasurfaces and thereby provides a paradigm for information security and anticounterfeiting.

Lithium Niobate Metasurfaces

“…Such distinct structural resonances of the LN metasurfaces provide accesses to artificial structural colors. As LN shows high transparency covering the visible spectral range, it is an ideal platform to realize the high‐efficiency structural colors in transmission mode, which is in remarkable contrast to the reflection colors demonstrated by the plasmonic, Si or perovskite‐based metasurfaces . The bright field transmission optical microscope images of a group of metasurfaces with period varying from 300 to 800 nm in 100 nm increment (duty cycle:62.5%) are shown in Figure a.…”

Reconfigurable Near‐field Enhancement with Hybrid Metal‐Dielectric Oligomers

“…Therefore, we work in non‐resonant conditions of irradiation and for this case the polarization of the laser beam does not affect the modification process. We should note that the influence of laser beam polarization on the modification process was shown to be critical for thin gold films or asymmetrical nanoantennas with different orientations with respect to the laser beam polarization, but can be neglected for symmetrical nanoantennas …”

Extrinsic Polarization‐Enabled Covert Plasmonic Colors Using Aluminum Nanostructures

“…By engineering the geometry of nanostructures and improving the material quality, such as roughness and grain boundaries, the chromaticity and brightness of structural colors have shown comparable performance with existing color display approaches . A plethora of structures has been proposed to generate vibrant colors, such as isolated nanopillars, metal–insulator–metal resonators, periodic arrays . The generated colors arise from either localized resonant modes or propagating resonant modes.…”