The ultimate goal of metasurface research in recent years is to apply metasurface to reality applications and improve the performance compared to its counterpart, namely conventional optical elements with the same function. Inspired by the application of electrically addressing spatial light modulator (EA-SLM) and based on the binary holographic algorithm, here we propose a reconfigurable metadevice integrated with the nematic liquid crystal (NLC). The smart metadevice directly uses the subwavelength antennas as the main contributor to the phase accumulation instead of the NLC layer. By applying different electrical modulation patterns on the NLC, the metadevice can realize the function of dynamic holographic display as traditional SLMs but features in smaller size, higher resolution and lager field of view. In addition, we improved the existing computer-generated hologram algorithm to generate three holograms with quantitative correlation and also propose a new optical encryption method based on our metadevice. The encryption method needs four elements in total to decrypt and can fully meets the requirements of the various encrypted content. We believe such metadevice paves the way for the new generation of micro-optical display and optical encryption devices.
Airy beams are widely used in various optical devices and optical experiments owing to their unique characteristics such as self-acceleration, self-recovery, and non-diffraction. Here we designed and demonstrated a metasurface capable of encoding two phase distributions independently in dual circular polarization channels. We experimentally observed the generated Airy beam arrays loaded on the metasurface in the real and K spaces. Compared with the traditional method, such method provides a more efficient solution to generate large capacity Airy beam arrays with switchable working modes in the broadband spectrum. The results may pave the way for the integration and miniaturization of micro-nano devices and provide a platform for information processing, particle manipulation, space–time optical wave packets, and Airy lasers.
Metalenses exhibit a substantial potential in replacing traditional optical component as they present a methodology for miniaturization. Lenses with tunable focal lengths can play a key role in various fields with applications in imaging, displays, and augmented and virtual reality devices. Here, we propose an electrically controllable varifocal metalens at the wavelength of 950 nm. The metasurface cascaded with nematic liquid crystal is integrated into an analog chip, which providing sequential specific two-dimensional addressable voltage patterns. The focal length of the reflective light can be modulated continuously with the change of voltage patterns. For the super-pixel cell with 6 μm period at a low voltage of 6 V, the zoom range and the zoom ratio are demonstrated to be 180 mm and 34, respectively. Besides, attributing to the enhanced forward scattering of Huygens metasurface and the large birefringence index of the liquid crystal, along with the integrated circuit compatible design, our metalens owns high integration in the NIR band under considering the practical processing. Therefore, the proposed nonmechanical varifocal metalens may unleash the full potential of continuous zoom metalens for micro-optical display and imaging applications in the future.
The fabrication of three-dimensional periodic microstructures with strong anisotropic geometries is important for nanophotonic devices including photonic crystals and hyperbolic metamaterials. In this study, a simple method using self-organizing colloidal inverse opals of PMMA with directional tensile deformation by stretching was successfully constructed in the temperature range 100°C-115°C. Reflection spectroscopy was used for investigating the photonic bandgap of the PMMA inverse opal with anisotropic geometries in anisotropic different extents. The wavelengths of the photonic band gap were related to both the length of the pores in long-axis and short-axis of pores of the inverse opals. The wavelength changes of the photonic band gap significantly affected by the length variation in the short-axis. The anisotropic optical properties were also observed when Ag and Pt were deposited onto the top surface or conformally coated onto the interior interfaces of the anisotropic inverse opals. The structures with higher anisotropic ratios showed stronger variations in the wavelengths of the reflection valleys according to the surface plasmonic polarizations and cut-off frequencies with varying polarization angles of incident light. Moreover, the PMMA inverse opals conformally coated with metals presented indefinite dielectric properties in the visible or near-infrared wavelength region.
Terahertz (THz) metasurfaces have emerged as powerful tools to modulate the wavefronts of THz radiation fully. Smart designs and fabrication are essential for enhancing the flexibility and encryption security of THz metasurfaces. In addition to digital coding metasurfaces and microelectromechanical systems, one method to realize dynamic THz metasurfaces is to utilize an active material. In this paper, a dynamic THz metasurface, which is combined with the phase‐change material VO2 and can be thermally controlled to achieve optical encryption, is proposed. Based on the electromagnetically induced transparency effect and by arranging the antennas in advance according to a specific hologram, a secret image can be encoded into the metasurface. At room temperature, the transmitted light field is an irregular light spot with no useful information. If the temperature increases above the phase‐change temperature, the encrypted hologram can be reconstructed. Moreover, owing to the distinct characteristics of VO2, the phase‐change temperature required during decryption is not very high, and the entire process is reversible. It is expected that, in combination with updated processing technology, such metasurfaces can be practically applied to the next generation of optical encryption or optical anticounterfeiting in the future.
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