High extinction ratio electromagnetically induced transparency analogue based on the radiation suppression of dark modes

A high extinction ratio (ER) electromagnetically induced transparency (EIT) analogue based on single-layer metamaterial is designed and experimentally demonstrated in this paper. This design involves four mirror-like symmetrically coupled split ring resonators (SRRs) that exhibit a bright-dark-dark-bright mode configuration. The EIT-like effect is realized by coupling between the bright resonators and dark resonators. The high ER feature is achieved from the suppression of radiative losses, due to opposite directions of electric and magnetic dipoles of two dark modes in the unit cell. Classical coupled resonator model is used to theoretically analyze the device transmission performances and to characterize parameter influence of the ER. Both numerical simulation and experiment results demonstrate that the ER of this device can reach more than 21 dB, which is 11 dB higher than that of conventional bright-dark coupling SRR arrangement. Finally, the potential multi-channel sensing utility of this device is demonstrated to show the importance of high ER feature.