Information encryption and security is a prerequisite for information technology, which can be realized by an optical metasurface owing to its arbitrary manipulation over the wavelength, polarization, phase, and amplitude of light. So far information encoding can be implemented by the metasurface in one-dimensional (1D) mode (either wavelength or polarization) only with several combinations of independent channels. Herein, we design dielectric metasurfaces by multiplexing for information encoding in a two-dimensional (2D) mode of both wavelength and polarization. Sixty-three combinations made out of six independent channels by two circular polarization states (RCP and LCP) and three visible wavelengths (633, 532, and 473 nm) are experimentally demonstrated, in sharp contrast with seven combinations by three independent channels in 1D mode. This 2D mode encoding strategy enhances the encryption security dramatically and paves a novel pathway for escalating the security level of information in multichannel information encryption, anticounterfeiting, optical data storage, and information processing.
We design and fabricate the Rochon-prism-like planar circularly polarized beam splitters based on dielectric metasurfaces by simultaneously controlling the geometric phase and the propagation phase via manipulation of the orientations and the sizes of the constituent silicon nanoblocks. The special splitters deviate only one of the circular polarizations while leave the other undeviated, acting like a Rochon prism for linearly polarized light, and their efficiencies can be as high as 66.7% with an extinction ratio of 27. The mechanism makes it possible to fabricate metasurface holograms that can only be reconstructed by either of two circular polarizations while hidden from the other. The functionality of beam splitting and polarization dependent decryption based on dielectric metasurfaces enables the potential applications in both miniaturized polarizing optical systems and information security and processing.
The possibility to
manipulate light fields with metasurfaces can
facilitate more compact and efficient devices for encoding computer-generated
holograms. However, most of the reconstructed holographic images for
reported metasurfaces are either monochromatic or two-dimensional,
limiting their applicability. Here, we design and fabricate a silicon
metasurface, whose constituent meta-molecules are composed of three
different kinds of meta-atoms capable of modulating red, green, and
blue light independently. A modified Gerchberg–Saxton algorithm
is utilized to retrieve the wavefront for the three-dimensional (3D)
hologram. The reconstructed 3D full-color images can be switched by
changing the helicity of the illuminating circularly polarized light.
The spin-switched 3D full-color scenes greatly increase the information
capacity of the device, which may find use in 3D dynamic displays,
virtual reality, and data storage applications.
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