基于柔性、非平面超表面的太赫兹调控机理与技术研究

Key functional devices are one of the bottlenecks that restrict the development of THz technology. The size of solid functional devices is very large, which is inconvenient for them to be integrated. The metasurfaces can control THz waves effectively in a very thin scale, so they have attracted much attention. But the current metasurfaces are mainly fabricated on the planar substrates, so their integration capability is still very weak. To deal with this problem, based on the basis of previous research on flexible and planar THz metasurfaces, the applicants propose to study the mechanism and technology of THz control based on flexible and nonplanar metasurfaces, including: analytically derive the theoretical model for ultra-thin metasurface control units integrated with carriers controlling THz waves, study the control mechanism and characteristics, and give the structure sizes of control units meeting the requirements under different incidence angles; then study and design the arrangement of control units in nonplanar metasurfaces; finally realize, in both theory and experiment, many kinds of controls for flexible and nonplanar metasurfaces integrated with lenses to THz waves, especially the control difficult to achieve for the single device. The metasurfaces studied can be easily integrated with nonplanar devices, so they can solve the actual problem that current THz metasurfaces lacks the integration capability, and the control function of the integrated device is stronger than the single one. Therefore, the studies in this project are of great scientific significance and application value in the field of THz control.

关键功能器件是制约THz技术发展的瓶颈因素之一。其中体功能器件尺寸较大，不便于集成；而超表面可在极薄的尺度内对THz波进行有效调控，所以倍受关注。但目前的超表面主要依托平面基底，因而可集成性仍显不足。针对这一问题，申请人基于前期对柔性、平面THz超表面的研究基础，提出研究基于柔性、非平面超表面的THz调控机理与技术，包括：解析推导集成于载体的超薄超表面调控单元对THz波进行调控的理论模型，并研究其调控机理与特性，给出在不同入射角度下满足调控要求的单元结构尺寸；进而研究设计非平面超表面中调控单元的排布；最终理论和实验实现集成于透镜的柔性、非平面超表面对THz波的多种调控，尤其是单个器件难以实现的调控。所研究的柔性超表面很容易与非平面器件集成，因而可以解决目前THz超表面可集成性不强的实际问题，并且集成之后的调控功能比单个器件更强，因此本项目研究在THz调控领域具有重要的科学意义和应用价值。

THz波在6G移动通信、生物医学及无损检测等领域有巨大的应用潜力，而THz超表面因其优越的电磁调控能力受到了广泛关注。该项目围绕THz超表面进行研究，所取得的主要研究成果包括：对基于超薄、柔性超表面的THz波调控进行了深入研究，利用其实现了对相位、振幅和极化的操控，并实现极化转换、平面透镜及艾里光束产生等一系列功能。进而将这种超表面集成于透镜一侧，形成共形超表面，并使垂直极化的THz波实现聚焦、贝塞尔波束产生和相位全息等调控功能，同时使水平极化的THz波通过柱透镜聚焦成一条线，实验测得的调控效率高达72%~88%。此外，这种柔性超表面具有可穿戴特性，可与不同传统器件进行集成以实现多种THz调控功能，并且器件有、无超表面两种工作模式可根据需要进行切换。提出了一种由新型金属孔功能基元序构构建的超表面，这种超表面可同时支持表面等离激元谐振模和两个正交极化的波导模式，其中表面等离激元谐振模主要影响调控效率，而两个波导模式可用来实现对THz波相位、振幅和极化的完全操控。尤其是，所用金属孔功能基元可实现对两正交极化波相位的独立、高效调控，这为THz波极化复用提供了便利。而且，这种极化复用不仅可在同一频带上实现，而且可在不同频带上实现。现已实验实现的调控功能有：双离轴聚焦、极化可切换的相位全息、双频极化分复用、矢量波束产生及正交光束分裂等。本项目的研究成果可有效促进THz核心器件的开发，对推动6G无线通信技术的发展具有十分重要的意义。