Abstract
We provide the first experimental demonstration of the handedness dependent electromagnetically induced transparency (EIT) in chiral metamaterials during the interaction with circularly polarized waves. The observed chiral-sensitive EIT phenomena arise from the coherent excitation of a non-radiative mode in the component split ring resonators (SRRs) produced by the corresponding Born−Kuhn type (radiative) resonators that are responsible for the pronounced chirality. The coherent coupling, which is dominated by the bonding and antibonding resonances of the Born−Kuhn type resonators, leads to an extremely steep dispersion for a circularly polarized wave of predefined handedness. Accordingly, retrieved effective medium parameters from simulated results further reveal a difference of 80 in the group indices for left- and right-handed circularly polarized waves at frequencies within the EIT window, which can potentially result in handedness-sensitive pulse delays. These chiral metamaterials which enable a handedness dependent EIT effect may provide more degrees of freedom for designing circular polarization based communication devices.
Highlights
Induced transparency (EIT), a macroscopic manifestation of quantum coherent interference, has been proposed and demonstrated in multi-level atomic systems
Subunits of systems for Metamaterial-induced transparency (MIT) are in general composed of two types of resonators which are arranged in an appropriate manner and responsible for the radiative and non-radiative modes respectively
It should be noted that in contrast to that of the plasmonic counterpart, absorption in the printed circuit board (PCB) technology based microwave metamaterials happens within the dielectric substrate rather than in the metallic portions of the structure which can be approximately treated as perfect electrical conductors (PECs)
Summary
Induced transparency (EIT), a macroscopic manifestation of quantum coherent interference, has been proposed and demonstrated in multi-level atomic systems. Born− Kuhn type resonators interact with circularly polarized electromagnetic waves to induce a chiral-sensitive non-radiative resonance in nearby split ring resonators (SRRs), which gives rise to the corresponding transparency window of a prescribed handedness. The coherent coupling between the Born− Kuhn type resonators and the SRRs results in an extremely steep dispersion of the circularly polarized waves, which facilitates the realization of a pronounced difference in group velocity for the opposite handedness. This class of hybrid chiral metamaterials can potentially enable ultracompact and handedness dependent delay lines for circularly polarized waves at prescribed frequencies
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