Metasurfaces have powerful light field manipulation capabilities and have been researched and developed extensively in various fields. With an increasing demand for diverse functionalities, terahertz (THz) metasurfaces are also expanding their domain. In particular, integrating different functionalities into a single device is a compelling domain in metasurfaces. In this work, we demonstrate a functionally decoupled THz metasurface that can incorporate any two functions into one metasurface and switch dynamically through external excitation. This proposed metasurface is formed by the combination of split-ring resonators and phase change material vanadium dioxide (VO2${\mathrm{VO}}_2$). It operates in the single-ring resonant mode and double-ring resonant mode with varying VO2${\mathrm{VO}}_2$ in insulating and metallic states, respectively. More importantly, the phase modulation is independent in two operating modes, and both cover a 360° cross-polarized phase with efficient polarization conversion. This characteristic makes it obtain arbitrary independent phase information on the metasurface with different modes to switch dual functions dynamically. Here, we experimentally demonstrate the functions of a tunable focal length and large-angle focus deflection of a THz off-axis parabolic mirror to verify the dual-function switching characteristics of the functionally decoupled metasurface. The functionally decoupled metasurface developed in this work broadens the way for the research and application of multifunctional modulation devices in the THz band.

中文翻译：

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通过双模去耦的动态双功能太赫兹超表面

超表面具有强大的光场操纵能力，并在各个领域得到了广泛的研究和开发。随着对各种功能的需求不断增加，太赫兹 (THz) 超表面也在扩展其领域。特别是，将不同的功能集成到单个设备中是超表面中一个引人注目的领域。在这项工作中，我们展示了一种功能解耦的太赫兹超表面，它可以将任何两个功能合并到一个超表面中，并通过外部激发动态切换。这个提出的超表面是由裂环谐振器和相变材料二氧化钒 ( VO 2${\mathrm{VO}}_2$ ) 的组合形成的。它以单环谐振模式和双环谐振模式运行，VO 2不同${\mathrm{VO}}_2$分别处于绝缘状态和金属状态。更重要的是，相位调制在两种工作模式下是独立的，并且都覆盖了 360° 交叉极化相位，具有高效的极化转换。这一特性使其能够在不同模式的超表面上获得任意独立的相位信息，从而动态切换双重功能。在这里，我们通过实验证明了太赫兹离轴抛物面镜的可调焦距和大角度聚焦偏转的功能，以验证功能解耦超表面的双功能切换特性。本工作开发的功能解耦超表面拓宽了太赫兹波段多功能调制器件的研究和应用途径。