基于超构表面色散特性的多波段电磁位相调控研究

Recent years have witnessed the rapid development of electromagnetic metasurfaces. By utilizing the phase engineering properties of subwavelength inclusions in the metasurfaces, it has been demonstrated that the limitations of traditional optical theory can be overcome, leading to a lot of miracles such as flat lens and high-efficient polarization conversion. However, traditional metasurfaces are suffering from its intrinsic strong dispersion. Since the phase shift of metasurface is close related to the frequency of incident radiation, it becomes hard to satisfy the requirement of broadband and multispectral applications emerging recently. In this project, we planned to give a deep research into the phase dispersion property of metasurface, remedy the flaw of traditional theory of metasurface, develop methods for dispersion engineering, and construct the mathematical and physical model for broadband and multispectral phase engineering. On the basis of our previous work, we would like to adopt new techniques and new-type subwavelength structures to construct functional devices such as flat lenses. Our project may break the limitations of traditional theory, and make profound impacts on the metasurface and related fields.

超构表面（metasurface）是光学和电磁学领域近年来发展起来的前沿方向。利用超构表面中亚波长结构的独特位相调制特性，可突破传统光学理论的限制，实现平面透镜、高效极化（或称偏振）转换。然而，超构表面具有内在的强烈色散，其位相特性与入射电磁波频率密切相关，难以满足现代电磁学宽光谱、多频段的应用需求。本项目拟针对上述问题，深入研究位相型超构表面的色散特性，弥补当前超构表面理论方面的不足，发展超构表面色散调控方法，建立宽带和多波段位相调控的数理模型。本项目拟在前期工作的基础上，基于新的亚波长结构设计思路，构建出能满足宽波段和多波长独立位相调控需求的亚波长结构，并完成平面光学器件的设计、加工以及实验验证。本项目有望突破传统电磁理论方法在位相调控方面的局限，对超构表面及相关领域产生重要而深远的影响。

本项目针对超构表面的色散和多波段电磁调控开展研究。利用超构表面中亚波长结构的独特位相调制特性，可实现平面透镜、偏振转换、自旋-轨道相互作用等器件和功能。然而，超构表面具有内在的强烈色散，其位相特性与入射电磁波频率密切相关。本项目针对上述问题，深入研究了位相型超构表面的色散特性，发展了超构表面色散调控方法，建立了宽带和多波段位相调控的数理模型，据此构建了左右旋独立调控、多波长独立调控、多谱段兼容调控、动态调控等位相型平面功能器件，为超构表面的实用化奠定了一定基础。具体而言，代表性成果包括：1）结合表面等离子体传输位相和几何位相，在可见光波段实现了对左右旋圆偏振光位相的独立调控，用于产生独立的轨道角动量，成果发表于ACS Photonics, 2016, 3: 2022–2029；2）提出介质型色散调控超构表面，实现多波长独立位相调控，成果发表于Optics Express, 2017, 25: 21419–21427；3）利用全金属亚波长结构中的几何位相，结合虚拟赋形技术，实现了多谱段（微波、红外和激光）特征的兼容调控。相关工作发表于Advanced Functional Materials, 2018, 28: 1706673等；4）利用相变材料GST，在红外波段实现了对几何位相的动态调控，能在不同状态下实现全息、轨道角动量等功能。成果发表于Advanced Science, 2018, 5: 1800835。