Wide-angle and polarization-independent electromagnetically induced transparency-like effect based on pentacyclic structure

A pentacyclic structure analog wide-angle and polarization-independent electromagnetically induced transparency-like (EIT-like) effect is numerically and experimentally demonstrated. The unit cell of the structure is composed of four identical circular inner rings surrounded by a larger circular outer ring. A wide-angle and polarization-independent transparency window is clearly observed in the spectral overlapping region of absorption bands of the inner and outer rings. The resonant feature of the transparency effect is investigated by the surface current distribution. We find that the coupling fields between rings play key roles and lead to the classical EIT-like effect. It is also shown that the polarization direction in our structure can be used to tune the position of the localized electric field enhancement. In addition, the effective group index and the effective refractive index are extracted to verify the slow light property with low loss. It is shown that our structure can reduce the group velocity of light by a factor of 64.