Abstract
Chiral metamaterials with asymmetric transmission can be applied as polarization-controlled devices. Here, a Mie-based dielectric metamaterial with a spacer exhibiting asymmetric transmission of linearly polarized waves at microwave frequencies was designed and demonstrated numerically. The unidirectional characteristic is attributed to the chirality of the metamolecule and the mutual excitation of the Mie resonances. Field distributions are simulated to investigate the underlying physical mechanism. Fano-type resonances emerge near the Mie resonances of the constituents and come from the destructive interference inside the structure. The near-field coupling further contributes to the asymmetric transmission. The influences of the lattice constant and the spacer thickness on the asymmetric characteristics were also analyzed by parameter sweeps. The proposed Mie-based metamaterial is of a simple structure, and it has the potential for applications in dielectric metadevices, such as high-performance polarization rotators.
Highlights
Optical diodes play a significant role in the application of optoelectronics and optical computing [1,2,3].Similar to the diodes in electronic components, they show different optical transmissions in two opposite directions
Illuminated by a photonic crystal [34], we have numerically demonstrated a bilayer Mie-based dielectric metamaterial working in the X-band, which exhibits a dual-band asymmetric transmission (AT) effect of linearly polarized waves
Fano resonances were found near the AT transmission peaks
Summary
Optical diodes play a significant role in the application of optoelectronics and optical computing [1,2,3].Similar to the diodes in electronic components, they show different optical transmissions in two opposite directions. Traditional diode-like optical or electromagnetic devices need to break the time reversal and spatial inversion symmetries simultaneously [4], which requires materials with specific optical properties. Chiral metamaterials, which are able to support asymmetric transmission (AT) for linearly or circularly polarized electromagnetic waves [5,6,7], provide a reciprocal route to mimic the unidirectional transmission feature of diodes. The metamaterial methods allow a free design of the metamolecules with extraordinary physical properties, such as negative refraction [8], reversed. The intriguing electromagnetic characteristics are attributed to the special-designed metallic or dielectric resonators. Metamaterials based on dielectric resonators are believed to show lower heat dissipation in higher frequencies [11,12]
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