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<p>With the rapid development of physical-layer information security, multi-user authentication, and multi-channel data storage, conventional coding metasurfaces that support only a single incidence direction or a single tuning degree of freedom are no longer adequate for the demanding requirements of high security, multi-dimensional information multiplexing, and dynamic tunability in complex scenarios. To address the limitation that most existing terahertz imaging metasurfaces can modulate information only for a single incident direction and struggle to simultaneously accommodate multiple directions, multiple polarizations, multiple coding states, and high-security encryption, this paper presents a dynamically tunable terahertz reflective metasurface based on vanadium dioxide (VO<sub>2</sub>) phase-change material, which enables multi-channel holographic imaging and physical-layer information encryption under bidirectional incidence. The metasurface adopts a sandwich configuration comprising upper and lower functional layers with an intermediate metallic reflector: the top layer integrates hybrid tunable units composed of VO<sub>2</sub> and metal, the bottom layer consists of metallic cross-shaped structures, and the middle metal film ensures bidirectional reflection capability. By tailoring the geometrical parameters of the unit cells, we establish phase-encoding unit libraries that are valid for different incident directions and different phase states of VO<sub>2</sub>. The imaging performance is then analyzed under various incidence directions, polarization states, frequencies, and temperature conditions, through array synthesis based on the phase distributions of the target patterns. Each imaging channel achieves full phase coverage from − π to π. Under backside incidence, the reflection amplitude exceeds 0.8 at 1.41 THz; under frontside incidence with VO<sub>2</sub> in the insulating state, the reflection amplitude exceeds 0.8 at 1.28 THz; and under frontside incidence with VO<sub>2</sub> in the metallic state, the resonance is dominated by the internal elliptical cross-shaped structure, with the reflection amplitude remaining above 0.5 at 1.54 THz—all of which meet the imaging requirements. Furthermore, under these conditions, dual-channel imaging can be realized via both X- and Y-polarized excitations. The total capability of independent information output across six channels endows the proposed metasurface with broad application prospects in areas such as physical-layer secure communication, multi-user identity authentication, high-security anti-counterfeiting, hierarchical access control, and high-capacity information storage.</p>

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Dynamically tunable terahertz bidirectional multi-channel holographic metasurface based on VO2 and its encryption application

  • 期刊论文

  • 发表日期：

    2026年7月31日

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  • Mengyuan Zhao,
  • Zeng Qu,
  • Yibin Gong,
  • Xuanqi Zhang,
  • Yuanhao Huang,
  • Peng Gao,
  • Bingxu Pan,
  • Jiayi Wang,
  • Xiaoyu Liu,
  • Yating Liu,
  • Jiayun Wang,
  • Xiaojun Shi,
  • Binzhen Zhang

摘要

With the rapid development of physical-layer information security, multi-user authentication, and multi-channel data storage, conventional coding metasurfaces that support only a single incidence direction or a single tuning degree of freedom are no longer adequate for the demanding requirements of high security, multi-dimensional information multiplexing, and dynamic tunability in complex scenarios. To address the limitation that most existing terahertz imaging metasurfaces can modulate information only for a single incident direction and struggle to simultaneously accommodate multiple directions, multiple polarizations, multiple coding states, and high-security encryption, this paper presents a dynamically tunable terahertz reflective metasurface based on vanadium dioxide (VO2) phase-change material, which enables multi-channel holographic imaging and physical-layer information encryption under bidirectional incidence. The metasurface adopts a sandwich configuration comprising upper and lower functional layers with an intermediate metallic reflector: the top layer integrates hybrid tunable units composed of VO2 and metal, the bottom layer consists of metallic cross-shaped structures, and the middle metal film ensures bidirectional reflection capability. By tailoring the geometrical parameters of the unit cells, we establish phase-encoding unit libraries that are valid for different incident directions and different phase states of VO2. The imaging performance is then analyzed under various incidence directions, polarization states, frequencies, and temperature conditions, through array synthesis based on the phase distributions of the target patterns. Each imaging channel achieves full phase coverage from − π to π. Under backside incidence, the reflection amplitude exceeds 0.8 at 1.41 THz; under frontside incidence with VO2 in the insulating state, the reflection amplitude exceeds 0.8 at 1.28 THz; and under frontside incidence with VO2 in the metallic state, the resonance is dominated by the internal elliptical cross-shaped structure, with the reflection amplitude remaining above 0.5 at 1.54 THz—all of which meet the imaging requirements. Furthermore, under these conditions, dual-channel imaging can be realized via both X- and Y-polarized excitations. The total capability of independent information output across six channels endows the proposed metasurface with broad application prospects in areas such as physical-layer secure communication, multi-user identity authentication, high-security anti-counterfeiting, hierarchical access control, and high-capacity information storage.