Polarization-insensitive electromagnetically induced transparency-like and dual-band absorption based on graphene and vanadium dioxide metamaterials

In this work, a dynamically tunable and polarization-insensitive electromagnetically induced transparency-like (EIT-like) and dual-band absorption based on graphene and vanadium dioxide metamaterial is proposed. The unit cell of the metamaterial consists of two monolayer graphene square rings of different sizes. The transparent window results from the near-field coupling can be observed in the x and y polarization directions, respectively. The EIT-like effect can be tuned by changing the Fermi energy of graphene. The three-level $\Lambda$-type system and the distribution of the electric field on $\left|E_z\right|$ are employed to explain the physical mechanism of the EIT-like effect clearly. The theoretical fitting results based on the coupled oscillator model are in good agreement with the numerical simulation results. In addition, by introducing vanadium dioxide (VO${}_2$) and utilizing the phase change property of VO${}_2$, the designed metamaterial can realize the transition from an analog of electromagnetically induced transparency to a dual-band absorber which has two absorption bands in the frequency range of 0.2–3 THz and the absorption rate reaches 63.2% at 0.96 THz and 99.6% at 1.89 THz. Furthermore, we investigate the performance of metamaterials to probe the refractive index of the surrounding medium and our prototype exhibits a highest sensitivity value of about 0.4845 THz/RIU. This proposed design provides a viable approach for developing slow-light devices, sensors, absorption, and multifunctional devices.