A reciprocity electromagnetically induced transparency (EIT) effect can be obtained in the complementary graphene metasurface structure. The EIT spectra can be obtained whether the excitation was input from a positive or reverse direction. The transmission of the structure which consisted of a graphene square (GS) and the graphene circle of hollowed air square (GCHAS) placed on the top and bottom of the polyimide layer was discussed. A wideband EIT window was found in the structure of GCHAS as bright mode and GS as dark mode by the finite integration time domain method. The EIT effect can be tuned by the chemical potential, the electron-phonon relaxation time of graphene, and the widths of GCHAS and GS, respectively. The polarization insensitive EIT effect can be obtained. The transmission mechanism is interpreted by giving the electric and magnetic field distributions at certain frequencies. The effective permittivity of the structure was calculated by method of inversion. These results can be applied for many areas, such as wideband wavelength slow-light devices, active plasmon switching and bidirectional devices.

A frequency-tunable cloak with semiconducting constituents has been proposed by modifying the dielectric constant by externally controlling the free-carrier density. We have theoretically studied that the cloaking frequency of a single-layer shell consisting of intrinsic InSb can be tuned by varying the temperature based on the Mie scattering theory. The calculated results show that this tunable cloak has a large bandwidth of over 0.3 THz, a tunability of cloaking frequency of 17 GHz K−1 with temperature and a dramatic reduction in the total scattering cross section of 90% at cloaking frequencies. It is also possible to realize a tunable cloak of extrinsic semiconductor Ge by changing the impurity density with current injection.

We have theoretically suggested a temperature-dependent superconducting cloak whose cloaking frequency can be externally controlled, since the dielectric constant of the superconductor is well tuned with the operating temperature. The results show that this tunable cloak exhibits a fine tunability in the low-temperature range 0–0.3 T c and a fast tunability in the high-temperature range 0.3T c–T c, together with a large reduction in scattering (<−50 dB). It may provide a potential way to design a tunable cloak with considerable flexibility.

We propose an invisibility multifrequency cloak with a single shell of negative index metamaterials (NIMs) based on the scattering cancellation cloaking theory. Theory and simulation results show that the cloak can reduce the total scattering cross section at multiple frequencies by exploiting the frequency dispersion of the permittivity and permeability simultaneously. It may provide a potential way to design a multifrequency cloak.

We investigate the existence and stability of surface defect gap solitons at an interface between a defect in a two-dimensional optical lattice and a uniform saturable Kerr nonlinear medium. The surface defect embedded in the two-dimensional optical lattice gives rise to some unique properties. It is interestingly found that for the negative defect, stable surface defect gap solitons can exist both in the semi-infinite gap and in the first gap. The deeper the negative defect, the narrower the stable region in the semi-infinite gap will be. For a positive defect, the surface defect gap solitons exist only in the semi-infinite gap and the stable region localizes in a low power region.