We presented a dynamically tunable electromagnetically induced reflection (EIR) based on the complementary graphene metamaterials composed of the wire-slot and split-ring resonators slot (SRRs-slot) array structures for the terahertz region. In this structure, the dark mode excited by the near field coupling between wire-slot and SRRs-slot structures, induces a reflection window. Moreover, the reflection window can be actively controlled by varying the lateral displacement between two slot-type resonant structures or Fermi energy of graphene without reoptimizing and re-fabricating structure. In addition, the large positive group delay obtained within the reflection peak can be also tuned over a broad terahertz region by changing the Fermi energy of graphene. Therefore, the work opens up the possibility for the development of compact elements such as modulators, tunable sensor, switches and slow light devices.

In this paper, we propose an ultrasensitive terahertz sensor based on the complementary graphene metamaterial composed of wire-slot and split-ring resonator slot array structure.

By patterning graphene on a SiO₂/Si substrate, in this paper, we designed and numerically investigated a terahertz electromagnetically induced transparency (EIT) graphene metamaterial, which consists of two coupled split ring resonators (SRRs) placed in an orthogonally twisted fashion, acting as the bright and dark elements, respectively. The calculated surface currents show that the dark mode excited by the near field coupling between two resonators can induce a distinct transparency peak in the transmission spectrum. Moreover, the amplitude and position of the transparency peak as well as the corresponding group delay can be actively tuned by changing the relaxation time or Fermi energy of graphene. Therefore, the graphene metamaterial with the actively tunable EIT peak exhibits potential applications in light storage, modulators, tunable sensors and switchers.

In microwave communication systems, focusing and imaging have attracted widespread attention due to their application prospects in the information processing and communication fields. Most existing multi-channel focusing and imaging are implemented by interleaved metasurfaces. However, the disadvantages of their large size and low efficiency limit their practical applications in large-capacity and low-loss integrated systems. To solve these issues, here, we propose a non-interleaved polarization-frequency multiplexing metasurface for high-efficiency multi-channel focusing and imaging. The meta-atoms of the non-interleaved metasurface are composed of a metallic ground plate, two dielectric layers, a larger cross-shaped metal structure, and a smaller cross-shaped metal structure embedded by a circular metal aperture. By altering the size of two cross-shaped structures, the designed meta-atom can obtain the independent complete 2π phase coverage with high reflection efficiency at two different frequency ranges for two orthogonal linear polarization (LP) incidences, realizing polarization multiplexing and frequency multiplexing. Moreover, two types of metasurfaces based on the above meta-atoms are designed to realize multi-channel focusing and imaging with high efficiency. As a proof, the focusing metasurface is fabricated and measured, and the measured results are well consistent with simulated results. Therefore, the proposed scheme has the advantages of high efficiency, multi-channel, and compact size, which possesses broad application prospects in low-loss and multi-channel communication integrated systems.

A novel graphene-based metamaterial absorber with actively tunable bandwidth, intensity and frequency, working at the terahertz (THz) spectral region, was designed and numerically investigated in this paper. The actively controlled absorption characteristics in the graphene absorber were achieved by integrating two identical-sized graphene disc elements to construct a supercell, in which two elements of all unit cells were connected respectively by the electrical isolation graphene wires to form selectively electrostatic doping. The surface current distributions and the circuit model analysis were conducted to reveal the absorption mechanism and predict the tuning mechanism. Moreover, by selectively tuning two gate voltages to change the Fermi energy reconfiguration state of two graphene elements, the absorption bandwidth, intensity and frequency of the metamaterial absorber could be actively controlled. In addition, a striking switching contrast was obtained by switching the reconfiguration state of the two discs. Therefore, this work paves a pathway for the realization of actively controlled terahertz waves based on electrically reconfigured graphene metamaterials.

In this paper, we numerically demonstrate that an actively controllable electromagnetic induced transparency (EIT) behavior can be obtained in a hybrid terahertz metamaterial. A unit cell of the hybrid metamaterial consists of a metallic split-ring resonator surrounded by a concentric graphene close-ring resonator, serving as superradiant and subradiant modes, respectively. The EIT-like effect results from the destructive interference caused by strong near field coupling between superradiant and subradiant mode resonators. A classical two-particle model is employed to theoretically study EIT-like behavior in the hybrid metamaterial, and the analytic results agree excellently with our numerical results. More importantly, by tuning Fermi energy based on electrical doping, the hybrid metamaterial can realize switching, modulation, and slow-light capabilities. Therefore, these results would exhibit potential applications in light storage and compact devices.