Metasurfaces can perform high-performance multi-functional integration by manipulating the abundant physical dimensions of light, demonstrating great potential in high-capacity information technologies. The orbital angular momentum (OAM) and spin angular momentum (SAM) dimensions have been respectively explored as the independent carrier for information multiplexing. However, fully managing these two intrinsic properties in information multiplexing remains elusive. Here, we propose the concept of angular momentum (AM) holography which can fully synergize these two fundamental dimensions to act as the information carrier, via a single-layer, non-interleaved metasurface. The underlying mechanism relies on independently controlling the two spin eigenstates and arbitrary overlaying them in each operation channel, thereby spatially modulating the resulting waveform at will. As a proof of concept, we demonstrate an AM meta-hologram allowing the reconstruction of two sets of holographic images, i.e., the spin-orbital locked and the spin-superimposed ones. Remarkably, leveraging the designed dual-functional AM meta-hologram, we demonstrate a novel optical nested encryption scheme, which is able to achieve parallel information transmission with ultra-high capacity and security. Our work opens a new avenue for optionally manipulating the AM, holding promising applications in the fields of optical communication, information security and quantum science.

Tunable metasurfaces provide a compact and efficient strategy for optical active wavefront shaping. Varifocal metalens is one of the most important applications. However, the existing tunable metalens rarely serves broadband wavelengths restricting their applications in broadband imaging and color display due to chromatic aberration. Herein, an electrically tunable polarization-multiplexed achromatic metalens integrated with twisted nematic liquid crystals (TNLCs) in the visible region is demonstrated. The phase profiles at different wavelengths under two orthogonal polarization channels are customized by the particle swarm optimization algorithm and matched with the dielectric metaunits database to achieve polarization-multiplexed achromatic performance. By combining the broadband linear polarization conversion ability of TNLC, the tunability of varifocal achromatic metalens is realized by applying different voltages. Further, the electrically tunable customized dispersion-manipulated metalens and switchable color metaholograms are demonstrated. The proposed devices will accelerate the application of metasurfaces in broadband zoom imaging, AR/VR displays and spectral detection.

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Mid-infrared large field-of-view (FOV) imaging optics play a vital role in infrared imaging and detection. The metalens, which is composed of subwavelength-arrayed structures, provides a new possibility for the miniaturization of large FOV imaging systems. However, the inaccuracy during fabrication is the main obstacle to developing practical uses for metalenses. Here, we introduce the principle and method of designing a large FOV doublet metalens at the mid-infrared band. Then, the quantitative relationship between the fabrication error and the performance of the doublet metalens with a large FOV from four different fabrication errors is explored by using the finite-difference time-domain method. The simulation results show that the inclined sidewall error has the greatest impact on the focusing performance, and the interlayer alignment error deforms the focusing beam and affects the focusing performance, while the spacer thickness error has almost no impact on the performance. The contents discussed in this paper can help manufacturers determine the allowable processing error range of the large FOV doublet metalens and the priority level for optimizing the process, which is of significance.

Metasurfaces can perform high-performance multi-functional integration by manipulating the abundant physical dimensions of light, demonstrating great potential in high-capacity information technologies. The orbital angular momentum (OAM) and spin angular momentum (SAM) dimensions have been respectively explored as the independent carrier for information multiplexing. However, fully managing these two intrinsic properties in information multiplexing remains elusive. Here, we propose the concept of angular momentum (AM) holography which can fully synergize these two fundamental dimensions to act as the information carrier, via a single-layer non-interleaved metasurface. The underlying mechanism relies on independently controlling the two spin eigenstates and arbitrary overlaying them in each operation channel, thereby spatially modulating the resulting waveform at will. As a proof of concept, we demonstrate an AM meta-hologram allowing the reconstruction of two sets of holographic images, i.e., the spin-orbital locked and the spin-superimposed ones. Remarkably, leveraging the designed dual-functional AM meta-hologram, we demonstrate a novel optical nested encryption scheme, which is able to achieve parallel information transmission with ultra-high capacity and security. Our work opens a new avenue for optionally manipulating the AM, holding promising applications in the fields of optical communication, information security and quantum science.