Luo Yuanda, Ye Wangcheng, Zhou Linjie, Xie Jingya
Opt Express. 2024 Jun 3;32(12):21216-21229. doi: 10.1364/OE.525377.
Metasurfaces are emerging as powerful tools for manipulating complex light fields, offering enhanced control in free space and on-chip waveguide applications. Their ability to customize refractive indices and dispersion properties opens up new possibilities in light guiding, yet their efficiency in exciting guided waves, particularly through metallic structures, is not fully explored. Here, we present a new method for exciting terahertz (THz) guided waves using Fabry-Perot (FP) cavity-assisted metasurfaces that enable spin-selective directional coupling and mode selection. Our design uses a substrate-free ridge silicon THz waveguide with air cladding and a supporting slab, incorporating placed metallic metasurfaces to exploit their unique interaction with the guided waves. With the silicon thin layer and air serving as an FP cavity, THz waves enter from the bottom of the device, thereby intensifying the impact of the metasurfaces. The inverse-structured complementary metasurface could enhance excitation performance. We demonstrate selective excitation of TE and TE modes with directional control, confirmed through simulations and experimental validations using a THz vector network analyzer (VNA) system. This work broadens the potential of metasurfaces for advanced THz waveguide technologies.
超表面正成为操纵复杂光场的强大工具，在自由空间和片上波导应用中提供了更强的控制能力。它们定制折射率和色散特性的能力为光导开辟了新的可能性，然而它们在激发导波方面的效率，特别是通过金属结构激发导波的效率，尚未得到充分探索。在这里，我们提出了一种使用法布里 - 珀罗（FP）腔辅助超表面激发太赫兹（THz）导波的新方法，该方法能够实现自旋选择性定向耦合和模式选择。我们的设计采用了具有空气包层和支撑平板的无衬底脊形硅太赫兹波导，并结合放置的金属超表面来利用它们与导波的独特相互作用。以硅薄层和空气作为FP腔，太赫兹波从器件底部进入，从而增强了超表面的影响。反向结构的互补超表面可以提高激发性能。我们通过使用太赫兹矢量网络分析仪（VNA）系统的模拟和实验验证，证明了对TE和TE模式的选择性激发以及定向控制。这项工作拓宽了超表面在先进太赫兹波导技术中的潜力。
