Slow light and absorption switchable terahertz metamaterials based on vanadium dioxide phase transformation properties

Versatile switchable terahertz devices have important applications in the field of terahertz technology, but it is currently difficult to implement them in a single device. In order to realize the switching between slow light and absorbing functions, a slow light and absorption switchable terahertz metamaterial based on the phase transition characteristics of vanadium dioxide (VO₂) is designed, which is composed of a top layer of aluminum (Al) square ring and a ring resonant unit, a middle layer of SiO₂ and a bottom layer of VO₂. Based on the electromagnetic field theory, the finite time domain difference (FDTD) method is used to simulate and analyze the optical properties of VO₂ in two states. When VO₂ is in the insulating state, the metamaterial can achieve a slow light effect with a maximum group delay of 2.85 ps, and when VO₂ is in the metallic state, the absorption rate of the metamaterial can reach 88.5% at 0.287 THz and 99.95% at 0.597 THz. We simulate the temperature-controlled phase transition process of VO₂ by changing the conductivity of VO₂, which can achieve the switching of slow light and absorption functions. In addition, we also found that the material is polarization insensitive. The metamaterial we have designed has some value in the research of terahertz multifunctional devices.