Spoof surface plasmon meta-couplers are compact antennas that link propagating waves and surface waves. However, most of them are designed with a fixed phase gradient and channel for the incident waves with specific polarization, which limits their further applications in multichannel scenarios. In this Letter, a new, to the best of our knowledge, method that combines the Brillouin zone folding theory with the generalized Snell’s law is proposed. We demonstrate that when the phase gradient of the metasurface is large enough, Brillouin zone folding effect will occur, which will create dual phase gradient space in a single metasurface. With this method, we design two novel terahertz meta-couplers with functionalities of symmetrical and asymmetrical binary-channel spoof surface plasmon (SSP) excitation. Furthermore, finite element method simulations are performed to demonstrate their functionalities. Considering the orthogonality of the incident waves, there can be a total of four independent space channels to excite SSPs on one metasurface. This work may open up new routes in multichannel SSP meta-couplers and multibeam surface wave antennas.

中文翻译：

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太赫兹双相梯度超表面：高效双通道欺骗表面等离子体激元激发

欺骗表面等离子体激元元耦合器是紧凑型天线，可将传播波和表面波链接在一起。然而，它们中的大多数被设计为具有特定偏振的入射波具有固定的相位梯度和通道，这限制了它们在多通道场景中的进一步应用。在这封信中，据我们所知，提出了一种新的方法，该方法将布里渊区折叠理论与广义斯涅尔定律相结合。我们证明，当超颖表面的相位梯度足够大时，布里渊区折叠效应就会发生，这将在单个超颖表面上产生双相梯度空间。用这种方法，我们设计了两个新颖的太赫兹元耦合器，它们具有对称和非对称二进制通道欺骗表面等离子体激元（SSP）激发的功能。此外，进行了有限元方法仿真以证明其功能。考虑到入射波的正交性，总共可以有四个独立的空间通道来激发一个超表面上的SSP。这项工作可能会为多通道SSP元耦合器和多波束表面波天线开辟新的途径。