image: Figure 1 Working schematic illustration of the dynamic holograms based on complete-basis-reprogrammable coding metasurface
Credit: OEA
A new publication from Opto-Electronic Advances; DOI 10.29026/oea.2024.240045, discusses complete-basis-reprogrammable coding metasurface for generating dynamically-controlled holograms under arbitrary polarization states.
This article proposes a dynamically-controlled holographic device based on complete-basis-reprogrammable coding metasurface. The orthogonal circular polarization components of the incident electromagnetic waves are utilized as a complete set of basis states, and the holographic image under arbitrarily polarized incident electromagnetic waves can be modulated and detected. Given the merits of rapid response, simple intergration, and high practicality, etc, the meta-device possesses great application potential in ultra-high capacity information storage, dynamic holographic display and detection, and multi-functional electromagnetic information processing.
Initially, the concept of digital and reprogrammable coding metasurfaces have been put forward to adopt binary codes to quantify physical parameters (e.g., amplitude, phase, and polarization). Compared with metasurfaces with continuously various parameters, they establish sound foundation for controlling complex electromagnetic operations in real time while simplifying the design of the electromagnetic waves. Among multitudinous studies of wavefronts shaping via reprogrammable coding metasurface, the most remarkable application is undoubtedly reprogrammable meta-holograms, on-demand recording, storage, and evocation of the targeted images, which meets the urgent needs of miniaturization, integration and tunability of photoelectric systems and holds great potential ranging from information encryption to intelligent detection. It’s easy to achieve independent control of multiple physical parameters under orthogonal linear polarization basis through reprogrammable coding metasurface with birefringent characteristics and further realize high-quality dynamic imaging and detection under different modes. However, birefringent reprogrammable coding metasurface generically requires more active components and works in a relatively narrow bandwidth and is inconducive to actual application of fabricated products. The spin-reprogrammable coding metasurface with high diffraction efficiency and wide operating bandwidth can reconstruct the electromagnetic characteristics under the orthogonal circular polarization basis via employing external excitations, which provides a novelty train of thought for the implemantation of simple dynamic holographic modulation, display and detection with encryptability, high convenience and large capacity in microwave band.
The authors of this article propose a dynamically-controlled holographic device based on complete-basis-reprogrammable coding metasurface, in which the orthogonal circular polarization components of the incident electromagnetic waves are utilized as a complete set of basis states. According to the vectorial synthesis and decomposition theory of electromagnetic field, the incident electromagnetic wave in any polarization state can be equivalent to the linear sum of this set of complete basis. In this study, they achieve independently dynamic regulation over the co-polarized reflection phases while maintaining the same amplitude for left-handed circularly polarized waves and right-handed circularly polarized waves via umbrella-shaped metallic structure embedded with two symmetrical positive–intrinsic–negative diodes which can be controlled through different voltages input from the field-programmable gate array. Correspondingly, combined with sequences calculated through iterative optimization algorithm, the target holographic imgae under arbitrarily polarized wave can be generated based on the joint coding and modulation of this complete set of basis. In both the simulations and experiments, they demonstrated four illustrative functionalities including spin-controlled meta-holograms with identical or variable focal length, coplanar dual-polarized pixel synthesis meta-holograms, and full-polarized detection system on Poincaré sphere, proving the the independent spin-space-addressing-multiplexing capability and puissant arbitrary polarization state adaptability and high robustness in dynamic holograms. Moreover, the entire meta-device possesses compact structure, broadband bandwidth, and high scalability.
The complete-basis-reprogrammable coding metasurface is dominated via voltage-controllable active components, which carries rapid response, simple integration and high practicability. It can be further linked with signal modulation and demodulation devices to achieve the transmission relay of the real images, and exhibits great application potential in ultra-high capacity information storage, dynamic holographic display and detection, and multi-functional electromagnetic information processing.
Keywords: basis vector control / reprogrammable metasurface / dynamically-controlled holograms / arbitrary polarization state / broadband
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The Artificial Structural Functional Materials Research Team at Air Force Engineering University is recognized as a leading basic research innovation team in Shaanxi Province. It is also designated as a Youth Innovation Team for universities in Shaanxi Province and a high-end platform construction team at Air Force Engineering University. The team is dedicated to addressing key national science and technology needs. Their core and distinctive research focus is on tackling critical challenges in the design, preparation, and application development of new artificial structural functional materials.
The team has published over 400 SCI papers in prestigious journals such as Nature Communications, Advanced Science, and Laser & Photonics Reviews, with more than 10,000 citations. They also authored the first monograph on metamaterial stealth technology in China and have been granted 33 national invention patents.
Their achievements include one first and one second prize of the Natural Science Award from the Ministry of Education, a first prize from the Shaanxi Province Natural Science Award, and three Outstanding Academic Paper Awards from Shaanxi Province. Additionally, graduate students from the team have received one National Excellent Doctoral Dissertation Award and one nomination. In recent years, the team has undertaken various national, military, provincial, and ministerial-level research projects, covering multiple research directions in artificial structural functional materials and their applications, leading to significant research outcomes.
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Chu ZT, Cai XQ, Zhu RC et al. Complete-basis-reprogrammable coding metasurface for generating dynamically-controlled holograms under arbitrary polarization states. Opto-Electron Adv 7, 240045 (2024). doi: 10.29026/oea.2024.240045