Theoretical proposal of electromagnetically induced transparency with a transmissive polarization conversion based on metamaterials

The polarization of electromagnetic waves is a key feature in the research areas of modern optics and information science. How to efficiently convert the polarization directions of the EM waves remains to be a challenge in electromagnetically induced transparency (EIT). Here, we theoretically propose a double-layer metamaterial with four symmetric H-shaped resonators, which can achieve the EIT phenomenon and transmissive linear polarization conversion (LPC). The EIT effect is acquired depending on the destructive interference between the electric and magnetic resonances. It is demonstrated that electromagnetic coupling is realized by reducing the structural symmetry of the rotated H-shaped resonators. Furthermore, the value of the maximum transmission coefficient reaches up to 0.900 at 14.202 GHz. The values of the transmission dips are 0.094 at 9.913 GHz and 0.176 at 16.101 GHz, respectively. Moreover, a broad transparency window that is higher than 0.8 can be gained spanning from 11.913 GHz to 15.289 GHz, and the relative bandwidth is 24.8%. Meanwhile, the momentous capability of the LPC is also observed. The transmissive cross-polarization conversion is well observed at 9.913 GHz and 16.101 GHz, where the polarization conversion ratios respectively are 90.2% and 91.8%. In the transparent window, a slow-light effect is highlighted. The values of the maximum group delay and group index respectively approach 91 ns and 1925. The FDTD simulation had been employed to further verify the effectiveness of group delay. In particular, the surface current distributions of the H-shaped resonators are employed to explain the mechanisms of the EIT effect and the transmissive LPC. Surpassing the general EIT structures and polarization converters, the proposed metamaterial is synchronously equipped with the EIT behavior and LPC by one same structure, which has numerous potential applications in communication and antenna technologies.