Terahertz Polarization Conversion in an Electromagnetically Induced Transparency (EIT)‐Like Metamaterial

Abstract In this paper, a unique metamaterial (MM) design incorporating both electromagnetically induced transparency (EIT) effect and polarization conversion is proposed. It consists of a cut‐wire as a bright resonator and a side coupled split‐ring resonator (SRR) as a dark resonator, on the one hand, the dark resonator can be excited by the bright resonator via the magnetic near‐field coupling, thereby contributing to a strong cross‐polarization conversion. On the other hand, the destructive interference between the sub‐radiant (dark) SRR and the super‐radiant (bright) cut‐wire results in an EIT effect. Benefiting from the destructive interference between the radiative and dark elements in the EIT MM, radiation loss is greatly suppressed and nearly perfect cross‐polarization conversion with high transmission and low‐loss is realized. In addition, the importance of symmetry is demonstrated by the phenomenon of polarization conversion and EIT effects disappearing when an identical cut‐wire is placed on the other side of the SRR. The proposed MM design provides a new way to address the loss problem in MM polarization devices. More importantly, this design principle of taking advantage of one area to solve the challenges in others may inspire new high‐performance multifunctional MM designs.