Coupling Plasmonic System for Complete Terahertz Amplitude and Phase Control of Co/Cross‐Polarized Reflection

ABSTRACT Recent advances prove that terahertz (THz) metasurfaces have become a main approach in manipulating THz propagations. The key lies in their flexibility in abruptly altering the local THz amplitude and phase responses. Previous studies predominantly rely on designing resonance/waveguide responses using a single structure, or employing interference among multiple structures to allow more controlling degrees of freedom. Here, we demonstrate that the coupling effect, commonly excluded in previous designs, can also be effectively utilized. This is demonstrated using a reflective metal‐insulator‐metal (MIM) configuration composed of two coupled C‐shaped split‐ring resonators (CSRRs) with the same and fixed dimensions. By simply varying their orientations, the coupling effect could assist to achieve complete THz amplitude and phase control in either co‐polarized or cross‐polarized channels in the linear polarization basis. The whole response and interplay can be analytically explained using the coupled‐mode theory (CMT). Six meta‐gratings are further proposed to validate the effectiveness. Our approach provides extensive potential for developing various THz functional devices.