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.

In this letter, we report a method of symmetry-breaking in an artificial Mie-based metamolecule.A Fano resonance with a Q factor of 96 is observed at microwave frequencies in a structure combining a split ring resonator (SRR) and a high-permittivity dielectric cube. Calculations indicate resonant frequency tunability will result from altering the cube's permittivity. The asymmetric spectrum is attributed to both constructive and destructive near-field interactions between the two distinct resonators. Experimental data and simulation results are in good agreement. The underlying physics is seen in field distribution and dipole analysis. This work substantiates an approach for the manipulation of Mie resonances which can potentially be utilized in light modulating and sensing.Metamaterials are artificial structures whose constituent units (metamolecules) have strong electromagnetic properties and are subwavelength in size. They have been the subject of much investigation over the past decade. They allow significant freedom of design, leading to rather intriguing physical properties such as negative refractive index 1,2 , and light transformation 3 . Based on various resonators, such as split ring resonators (SRRs) or variants, electromagnetic metamaterials are able to function as invisible cloaks 4,5 , and perfect lenses 2 .The Fano resonance, a quantum phenomenon exhibiting a non-Lorentzian spectral shape 6,7 and closely related to electromagnetically induced transparency (EIT), can be obtained by a symmetry-breaking method 8-12 in metamaterials. In this way, a dark mode is able to interfere a)

A magnetic tunable Fano-resonant metamaterial structure with enhanced nonreciprocity at microwave frequencies has been designed and investigated. The metamolecule has been implemented by using a dielectric cube and a magnetically biased ferrite. The Fano resonances originate from mode coupling between two constituents. The structure possesses a nonreciprocal feature since the external field breaks the time-reversal symmetry, and the Fano-type interference further enhances the nonreciprocal nature of biased ferrite. We are able to manipulate the Fano modes by adjusting the applied magnetic field. Simulation results suggest that the proper permittivity of the dielectric cube will optimize the nonreciprocal contrast. The magnetically tunable feature of the proposed metamaterial can potentially be applied to design dynamically controlled switches and isolators.

The Mie resonance of two dielectric meta-atoms causes a destructive coupling effect between them and results in hybridization induced transparency in the metamolecule. By actively adjusting the temperature, permittivities of the dielectric with opposite temperature coefficients vary in contrary trends, appearing as the field redistribution in each meta-atom. At the same time, two collective modes of the metamolecule behave as addition and subtraction of magnetic fields in meta-atoms. Combining both the intrinsic properties of materials and the collective properties of the coupling “dimer” system together, varying degrees of asymmetry of the metamolecule are obtained as the temperature changes. Since the intensity of the excited magnetic field can reflect the resonance amplitudes of the metamolecule onto the incident wave, the ratio of the transmission amplitudes of the two collective modes changes in a manner similar to the average magnetic field intensity of the metamolecule in two hybridized modes. Based on this behavior, we propose a method to estimate the degree of asymmetry of the metamolecule according to the field distribution intensity.

Hybridized metamaterials with collective mode resonance are usually applied as sensors. In this paper, we make use of one Mie-based hybridized metamolecule comprising of dielectric meta-atoms and an elastic bonding layer in order to detect the distances and applied forces. The hybridization induced splitting results in two new collective resonance modes, of which the red-shifted mode behaves as the in-phase oscillation of two meta-atoms. Owing to the synergy of the oscillation, the in-phase resonance appears as a deep dip with a relatively high Q-factor and figure of merit (FoM). By exerting an external force, namely by adjusting the thickness of the bonding layer, the coupling strength of the metamolecule is changed. As the coupling strength increases, the first collective mode dip red-shifts increasingly toward lower frequencies. By fitting the relationship of the distance–frequency shift and the force–frequency shift, the metamolecule can be used as a sensor to characterize tiny displacement and a relatively wide range of applied force in civil engineering and biological engineering.