Manipulations of light–matter interaction via sub-wavelength plasmonic structures have opened up many new research opportunities in photonics from microwave to the visible spectrum, including the relatively underdeveloped but technologically important terahertz regime. Here, we have studied manipulation of terahertz transmission through a bilayer metasurface consisting of a metallic hole array and a complimentary patch array separated by an ultra-thin dielectric spacer. The terahertz transmission spectra through our studied metasurfaces exhibit characteristic resonances due to the surface plasmon induced extraordinary transmission peak. Our study reveals a counterintuitive blue shift of the transmission peak with increasing spacer thickness, which is explained by reduced Coulomb interaction between two plasmonic layers. The measured quality factor exhibits a strong dependence on the spacer thickness, and the maximum quality factor is observed for a spacer thickness of around λ/30, indicating strong electric-field confinement inside the dielectric spacer. These bilayer plasmonic structures will aid in realizing next-generation terahertz plasmonic devices such as ultrasensitive thin-film sensors, modulators, narrow-band filters, and other nonlinear components.

通过亚波长等离激元结构对光-物质相互作用的操纵为光子学从微波到可见光谱打开了许多新的研究机会，包括相对欠发达但技术上很重要的太赫兹体系。在这里，我们研究了通过双层超颖表面的太赫兹传输的操纵，该超颖表面由金属孔阵列和由超薄介电垫片隔开的互补贴片阵列组成。由于表面等离子体激元引起的非凡透射峰，通过我们研究的超表面的太赫兹透射光谱表现出特征性的共振。我们的研究表明，随着间隔层厚度的增加，传输峰的蓝移与直觉背道而驰，这可以通过减少两个等离激元层之间的库仑相互作用来解释。所测得的品质因数表现出对隔离物厚度的强烈依赖性，并且对于约λ/ 30的隔离物厚度观察到最大品质因数，表明电介质隔离物内部的电场受限。这些双层等离激元结构将有助于实现下一代太赫兹等离激元设备，例如超灵敏薄膜传感器，调制器，窄带滤波器和其他非线性组件。