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With the rise of artificial magnetism and metamaterials, toroidal resonance has gained much attention for its special properties. In this paper, we propose a novel hybrid graphene-metal metamolecule consisting of a square bracket-like resonator and two asymmetric U-shaped resonators. By applying various Fermi energies to graphene, the amplitude of electromagnetically induced transparency (EIT) can be efficiently manipulated, and the maximum amplitude modulation depth can attain 81% in the microwave region. Numerical simulations and theoretical analysis demonstrate that the dynamic manipulation is mainly induced by the active tuning toroidal resonance through the recombination effect of the conductive graphene. Also, the maximum group delay of 85 ps can be attained and controlled with the increasing Fermi energy. The proposed hybrid graphene-metal metamolecule and dynamically manipulating mode presents a novel modulating strategy of EIT-like analog based on the toroidal response, which has great application for the design of efficient tunable resonators, filters, and sensors. [ABSTRACT FROM AUTHOR]

We present the design of a new type of irregular metamaterial structure that can achieve ultra-wideband absorption. The structure is created using 3D-printing to create a shell and contains multiple layers of water. The structure can achieve absorption levels greater than 0.9 in the 6.8–21.0 GHz range, with a relative bandwidth of 101.93%. The absorber also works in a wide range of incidence angles with different modes and is polarization insensitive. Measurement results obtained from a microwave experiment coincide well with the simulation results. The proposed metamaterial could be broadly applied in various civilian and military products in the future. [ABSTRACT FROM AUTHOR]

In this paper, a low-loss toroidal dipole metamaterial composed of four metal split ring resonators is proposed and verified at microwave range. Dual-band Fano resonances could be excited by normal incident electromagnetic waves at 6 GHz and 7.23 GHz. Analysis of the current distribution at the resonance frequency and the scattered power of multipoles shows that both Fano resonances derive from the predominant novel toroidal dipole. The simulation results exhibit that the sensitivity to refractive index of the analyte is 1.56 GHz/RIU and 1.8 GHz/RIU. Meanwhile, the group delay at two Fano peaks can reach to 11.38 ns and 12.85 ns, which means the presented toroidal metamaterial has significant slow light effects. The proposed dual-band toroidal dipole metamaterial may offer a new path for designing ultra-sensitive sensors, filters, modulators, slow light devices, and so on. [ABSTRACT FROM AUTHOR]

A double E-shaped toroidal dipole metasurface is designed with the high Q-factor Fano and classical electromagnetically induced transparency (EIT) phenomena in the microwave frequency range. With the introduction of an asymmetric structure, the sharp Fano resonance can be excited and acquired a quite high Q-factor of 134 at a lower frequency of 4.58 GHz. It can be numerically and experimentally demonstrated that the singularity Fano response of designed construction is caused by the intensive toroidal dipole. In addition, due to destructive interference between the intensive toroidal dipole and electric dipole, the transmission peak of EIT can reach 0.95 with a Q-factor of 50 at 10.18 GHz. By calculating and comparing the radiated power of multipoles, the enhanced toroidal dipole response can be further verified. The designed planar toroidal dipole metamaterial with simple construction may have many possible applications in toroidal moment generators, sensing, and slow-light devices. [ABSTRACT FROM AUTHOR]

Highlight • We proposed tunable and polarization sensitive electromagnetically induced transparency metamaterial. • When incident angles vary from 0° to 60°, the transmission spectra has two transmission windows in TE mode. • In TM mode, the transmission window has broadened in the transmission spectra. • On the other hand, the proposed metamaterial has slow light effect and the largest value of group index is 30 in the transparency peak. • According to the property of the designed metamaterial, we believe it suggests the future possibility for a new type of applications in sensing and filtering device. Abstract We demonstrate a classical analogue of electromagnetically induced transparency (EIT) metamaterial that consisting of anomalous split resonance ring and cross-shaped wire with simulations and experiments. The transmission spectrum is tunable with the incident angles varies from 0° to 60° in different modes. Under normal incident wave, the metamaterial leads to polarization insensitive EIT-like effect. The distributions of surface current at peaks and dips of transmission have been analyzed. Furthermore, the group index presents maximum at the transparency peak, which verifies the slow light effect. The proposed metamaterial could provide an avenue for various applications, such as refractive index sensor and microwave switch. [ABSTRACT FROM AUTHOR]

A compact planar construction composed of asymmetric split ring resonators was designed with a low-loss, high Q-factor resonance transparency at microwave frequency. The singularity property of the proposed metamaterial owing to the enhanced toroidal dipole T is demonstrated via numerical and experimental methods. The transmission peak can reach up to 0.91 and the loss is perfectly repressed, which can be testified by radiated power, H-field distributions, and the imaginary parts of effective permittivity and permeability. The designed planar metamaterial may have numerous potential applications at microwave, terahertz, and optical frequency, e.g., for ultrasensitive sensing, slow-light devices, lasing spacers, even invisible information transfer. [ABSTRACT FROM AUTHOR]