Multiplexing Vectorial Holographic Images with Arbitrary Metaholograms

Abstract

Metasurfaces achieving arbitrary phase profiles within ultrathin thickness, emerge as miniaturized, ultracompact, and kaleidoscopic nanophotonic platforms. However, it is often required to segment or interleave independent subarray metasurfaces to multiplex holograms in a single nanodevice, which in turn affects the device's compactness and channel capacity. Here, a flexible strategy is proposed for multiplexing vectorial holographic images by controlling the phase distributions of holographic images in far field. Benefitting from precisely controlling the phase difference of reconstructed images through the modified Gerchberg–Saxton algorithm, two different holographic images are independently designed for the circular light by two interleaved metasurfaces and an extra vectorial hologram is flexibly encrypted in far field without additional set of structures on the metasurface plane. An unlimited number of polarization can be achieved in the holographic image and additional information can be decrypted when different polarization‐dependent holographic images overlap. By continually varying phase difference between the incident right and left circular polarized light, the image within the overlap area can be modulated. The silicon dielectric metahologram with record absolute multiplexed efficiency (>25%) is achieved in the experiment. This technique, as far as it is known, promises an enormous data capacity as well as a high level of information security.

Tunable Full‐Color Vectorial Meta‐Holography

“…Other polarization light can also be used and analyzed in the similar way. The complex amplitude $$\overrightarrow {PA} $$ at the overlapping area can be obtained, [ 45,48 ] $$\[ \begin{array}{*{20}{c}}{\overrightarrow {PA} = {{\overrightarrow {PA} }_{\rm{t}}} + {{\overrightarrow {PA} }_{\rm{c}}}}\end{array} \]$$ $$\[ \begin{array}{*{20}{c}}{{{\overrightarrow {PA} }_{\rm{t}}} = \frac{{\sqrt 2 }}{2}{e^{i{\theta _{\rm{p}}}}}{e^{{\rm{i}}{\Phi _{\rm{L}}}}}\left( {{A_{tR}}{e^{ - i2{\theta _{\rm{p}}}}}{e^{i\Delta \Phi }}\overrightarrow L + {A_{tL}}\overrightarrow R } \right)}\end{array} \]$$ $$\[ \be...$$…”

“…To precisely manipulate the spatial polarization on the imaging plane, we adopt a modified GS algorithm [ 48 ] to control the phase difference of circularly polarized holographic images at the pixel scale (see Note S1, Supporting Information). As shown in Figure 2b, an image “chameleon” with spatial phase differences ΔΦ R , ΔΦ G , and ΔΦ B from 0 to π is designed to control the polarization of the reconstructed image in pixels.…”

“…One is to divide vectorial holographic images into several portions and the uniform polarization in each portion is determined by the corresponding subarray on the metasurface so the number of the polarization states is limited. [42][43][44] The other is that the polarizations of reconstructed images are spatially manipulated with high resolution by directly controlling the phase difference of orthogonal polarizations in far field, [45][46][47][48] which generally requires two or more sets of nanostructures for monochromatic vectorial holograms. Nevertheless, if it is directly adopted in the full-color vectorial hologram by increasing unit cells to independently control multi-wavelengths, high-order images would be inevitable because the period of meta-molecules will be larger than the working wavelength.…”

Bilayer‐Metasurface Design, Fabrication, and Functionalization for Full‐Space Light Manipulation

“…Metasurfaces have been employed to precisely control the amplitude, [ 1–5 ] phase, [ 6–11 ] polarization, [ 12–17 ] and frequency [ 18–20 ] of incident light at the subwavelength resolution. Thanks to the powerful point‐to‐point manipulation capabilities at the subwavelength level of metasurfaces, lots of novel optical elements and devices including metalenses, [ 21–27 ] nanoprints, [ 28–34 ] meta‐gratings, [ 35–37 ] vortex‐beam generators, [ 38–41 ] meta‐holograms, [ 42–48 ] and encryption displays [ 49,50 ] have emerged over the past decade. However, due to the limited degrees of freedom of nanostructures, current light manipulation with metasurfaces is usually conducted in either transmission or reflection space while the other half of space is abandoned, which may hinder the improvement of information density and functionality of metasurfaces.…”

Multiplexed Generation of Generalized Vortex Beams with On‐Demand Intensity Profiles Based on Metasurfaces

“…[ 19–23 ] Through delicate structural design of the meta‐atoms, a single metasurface can exhibit multiple polarization manipulation channels. [ 24,25 ] Such polarization multiplexing can be used for dynamic vectorial optical holography [ 26,27 ] and complicated structured light generation based on spin to angular momentum conversion. [ 28–31 ] Meanwhile, metasurfaces can also function as optical modulators for multiplexing and demultiplexing of the OAM channels of VB, [ 17 ] which facilitate information storage and transmission with different OAM channels.…”