Photocatalytic degradation of RhB for all samples under simulated solar light illumination and absorption spectra of RhB over 15 wt% SrTiO₃/NiFe₂O₄ nanocomposites.

In this paper, we theoretically and numerically demonstrate a polarization-controlled dynamically tunable electromagnetically induced transparency-like (EIT-like) effect based on graphene metasurfaces. The unit cell of metasurface is composed of a rectangular graphene ring placed between two parallel graphene strips, which can achieve tunable spectral responses in different polarization directions. And when the polarization angle of the incident light changes gradually from 0 to 90, the number of transparent windows can be switched between 1 and 2. The theoretical calculations based on the coupled Lorentz oscillator models have an excellent agreement with the simulation results. The mechanism of the dynamical modulation is attributable to the near field coupling of resonator units. Moreover, we can significantly adjust the transparency windows of the EIT-like by changing the asymmetry parameter and the Fermi level of graphene. Also, the strong dispersion and tunable group delay accompanied with the transparency window can be achieved for slow light application. Our proposed graphene metasurface architecture provides a new platform of multi-controlled EIT-like system for applications in slow light, optical sensor and selective filter.

We present numerical and theoretical analysis of the tunable electromagnetically induced transparency-like—EIT-like-effect based on graphene metasurfaces. The unit cells of metasurfaces are composed of a pair of parallel graphene strips and a two-split rectangular graphene ring resonator, both of which are performed as bright modes. The physical mechanism behind the EIT-like effect results from the frequency detuning and hybridization coupling of two bright modes. The FDTD simulation results show an excellent agreement with the theoretical analysis based on the coupled Lorentz oscillators model. Moreover, the transparency window of EIT-like effect can be modulated not only by changing the geometry of the nanostructure, but also by adjusting the Fermi level of graphene, allowing for an actively tunable group time delay of the light. In addition, owing to the peak frequency of the transparency window is highly sensitive to the variation of refractive index of the surrounding media, we demonstrate a refractive index sensor with sensitivity of ~ 6800 nm/RIU, and the calculated FOM can reach up to about 14.2. Therefore, our proposed nanostructure provides a feasible platform for slow light and sensing applications.

XRD patterns of pure AgBr, Bi ₂₄ O ₃₁ Br ₁₀ and AgBr/Bi ₂₄ O ₃₁ Br ₁₀ nanocomposites.