PIT-like effect in asymmetric and symmetric C-shaped metamaterials

Abstract

We present asymmetric and symmetric couplings within a pair of C-shaped resonators (CSRs). The former shows that a typical and prominent plasmon-induced transparency (PIT) spectral response can be observed and it stems from asymmetrically coupled resonance (ACR) between the subradiant and superradiant modes due to exactly identical resonance frequency but different quality factors (Q-factor). The mechanism of such induced transparency is elucidated well by resonant hybridization and the induced currents within the CSRs. Simultaneously, we find that PIT-like effect can also be achieved in symmetric CSRs, symmetrically coupled resonance (SCR) between the subradiant and superradiant modes also give rise to transparency window. Essentially, the phase coupling of near-field, besides symmetry or asymmetry, is the crux of the PIT. Comparing the transparency window in asymmetric coupling, the PIT-like effect in symmetric coupling becomes less strong than the former. We consider that a broken symmetry is not the only prerequisite for PIT-like effect; but it plays an important role of prominent PIT-like transparency window. This not only sharpens our understanding of the existing concept, but also provides a profound insight into the plasmonic coherent interference in the near-field zone.