An electromagnetically induced transparency metamaterial with polarization insensitivity based on multi-quasi-dark modes

To investigate the polarization and angle insensitive mechanism of an electromagnetically induced transparency (EIT) metamaterial, we designed, fabricated and measured a planar symmetry metamaterial structure. The planar symmetry metamaterial's cell consists of eight identical inner rings surrounded by a bigger outer ring, which serve as multi-quasi-dark elements and a bright element, respectively. A polarization and angle insensitive transparency window is clearly observed in the spectrum owing to the coupling between the multi-quasi-dark modes and the bright mode, which is verified by numerical simulations and experiments. A wider angle consistency is achieved because the multi-quasi-dark modes commonly participate in the destructive interference of scattering field. In addition, the excited principle and the resonance nature of EIT-like effects are investigated numerically. Simulation results show that the EIT-like effect is associated with the anti-symmetry current, which is induced by coupling fields introducing the phase delay. Finally, the slow wave property of the metamaterial is verified by numerical simulation.