Spatial Frequency Multiplexed Meta-Holography and Meta-Nanoprinting

Abstract

Metasurfaces are flat structured surfaces that are designed to control the two-dimensional distributions of phase, polarization, and intensity profiles of optical waves. Usually, the optical response of metasurfaces is dispersive and polarization-dependent, which indicates the capability of using metasurfaces for information multiplexing using wavelengths and polarization states. However, most multiplexing techniques based on metasurfaces reported so far occur only in the spatial domain. Here, we experimentally demonstrate metasurface multiplexing by exploiting the degree of freedom of the spatial frequency domain. Specifically, we overlap two independent holographic images at high and low spatial frequencies and record them onto a single piece of metasurface hologram (meta-hologram). These two holographic images can be successfully separated from the reconstructed overlapped images by using two digital Gaussian filters. In addition, we demonstrate spatial frequency multiplexing by meta-nanoprinting, in which a complex multiplexed image (the combination of a cat image and a dog image) is recorded and demultiplexed with high fidelity. The presented spatial frequency multiplexing with metasurfaces suggests a route to increase the information channel and may contribute to the research and applications in optical information encoding, optical storage, optical information hiding, information security, compact displays, etc.

Integrated Metasurfaces with Microprints and Helicity‐Multiplexed Holograms for Real‐Time Optical Encryption

“…Microprint and holography are often used as two separate optical encryption strategies applied in independent metasurface devices, which can be achieved by controlling over plasmonic [ 29–34 ] or all‐dielectric [ 35–40 ] structures at the nanoscale. To strengthen optical information security, other parametric freedoms such as polarization, [ 41–45 ] wavelength, [ 17,46–49 ] and spatial freedom [ 50–52 ] have been explored to achieve multiplexed microprint or holography encryption devices. Very recently, attempts have been implemented to combine the microprint and holography in a single device.…”

Optical Metasurfaces for Generation and Superposition of Optical Ring Vortex Beams

“…[6] Optical metasurfaces are planar analogy of metamaterials with exotic optical properties, which are able to control light's propagation in a desirable manner. [7][8][9][10][11][12][13] The ultrathin nature of optical metasurfaces provides a much compact platform to generate [14] and manipulate OAM beams. [15][16][17][18] However, for the mentioned applications in optical communications, usually based on fibers, one needs to match the radial size of the OAM beams (a doughnut shape) to the size of an optical fiber and this strongly depends on the TC of the OAM beam.…”

Printing polarization and phase at the optical diffraction limit: near- and far-field optical encryption

“…A great deal of attention has been paid on the design of light source-dependent meta-hologram, such as polarization selectivity [30][31][32][33], orbital angular momentum selectivity [34,35], incoming direction of the incident light [36][37][38], etc. Other attempts have also been made for metasurface encryption, such as the combination of color printing and the holographic image [39,40], image postprocessing based on spatial frequency [41], and tunable meta-hologram [42]. All of the proposed metasurface encryptions, relying either on the intensity of the color print or on the holographic image projection, are directly perceived by human eyes, which could limit their applicability for information security.…”