Abstract Metasurfaces exhibit flexible functional tunability by importing phase change materials. However, in most cases, these metasurfaces work in either transmission mode or reflection mode, which limits the application in function integration. Aiming at functions integration, a novel metasurface is proposed to realize the invertible transition between transmission and reflection modes in terahertz (THz) frequencies by utilizing a structured vanadium dioxide (VO2). The wavefronts of the transmission and reflection modes can be independently manipulated according to the insulator-metal phase transition induced simply by the temperature, allowing the integration of expanded functions. As an example of the functionality, a highly efficient, polarization-independent, and bifunctional metasurface with a lens in the transmission mode and a half-wave plate in the reflection mode has been designed and numerically demonstrated. The focusing efficiency of the meta-lens reaches to 68% with focal spot size exceeding the calculated diffraction limit at frequency of 1.4 THz, and the polarization conversion rate of the half-wave plate is higher than 90% within frequency width of 0.44 THz. The proposed tunable metasurface provides a simple way to develop high-performance multifunctional metadevice.

中文翻译：

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在透射和反射模式下具有独立控制和可切换功能的高效太赫兹超表面

摘要 超表面通过导入相变材料表现出灵活的功能可调性。然而，在大多数情况下，这些超表面要么以透射模式工作，要么以反射模式工作，这限制了在功能集成中的应用。针对功能集成，提出了一种新型超表面，利用结构化二氧化钒 (VO2) 实现太赫兹 (THz) 频率传输和反射模式之间的可逆转换。传输和反射模式的波前可以根据简单地由温度引起的绝缘体-金属相变独立操纵，从而允许扩展功能的集成。作为功​​能的一个例子，一个高效的、偏振无关的、已经设计并数值证明了具有透射模式的透镜和反射模式的半波片的双功能超表面。超透镜聚焦效率达到68%，焦斑尺寸在1.4 THz频率下超过计算衍射极限，半波片偏振转换率在0.44 THz频宽内高于90%。所提出的可调超表面提供了一种开发高性能多功能超器件的简单方法。44 太赫兹。所提出的可调超表面提供了一种开发高性能多功能超器件的简单方法。44 太赫兹。所提出的可调超表面提供了一种开发高性能多功能超器件的简单方法。