Research Of Tunable Metamaterials Based On VO₂ In Terahertz Range

Metamaterial is a kind of artificial composite materials of which designers can strictly design periodical or non-periodical artificial micro-structure units and arrange them in a certain regular pattern at the atomic or molecular level according to the subjective will.The application of the terahertz band is a hot topic at home and abroad.The combination of phase-change material VO₂ and metamaterial greatly enhances the tunability of metamaterials.In this paper,four kinds of tunable metamaterials based on VO₂ are designed.They can achieve good adjustability in the terahertz band.The first kind of metamaterial designed in this paper is based on VO₂ multi-layer split resonant ring terahertz adjustable metamaterial.This type of VO₂-based multi-layer split resonant ring terahertz metamaterial will produce different resonant modes with the change of the VO₂ conductivity filled in resonant ring opening.So VO₂ can be used to dynamically control the transmission of this kind of metamaterial.The enhancement of the electric field at the opening of the resonant ring changes significantly with the generation of the VO₂ phase transition and the electric field enhancement effect of this metamaterial can be dynamically controlled using VO₂.The second kind of VO₂-based metamaterial designed in this paper is an asymmetric Au and VO₂ double-bar multi-layer terahertz-tunable metamaterial.When VO₂ is in the metallic state,the transmission spectrum and absorption spectrum of this metamaterial are found to exhibit an asymmetrical line shape resembling Fano resonance.A magnetic field diagram of the surface of this material was studied and it was found that the dipole resonance interaction between the Au strip and the metallic VO₂ strip led to the Fano resonance of the system.The magnetic field enhancement between the Au strips and the metal VO₂ strips indicates that this metamaterial can support relatively high quality Fano resonances.The third kind of VO₂-based metamaterial designed in this paper is VO₂/Au strip type multi-layer magnetic resonance band structure terahertz adjustable metamaterial.The transmittance of this kind of metamaterial can be dynamically controlled by changing the VO₂conductivity.The magnetic field intensity of the gap between the Au strip and the VO₂ strip at1.03 THz and 1.41 THz was studied.It was found that the VO₂/Au strip type multilayer artificial electromagnetic material supports magnetic resonance in the terahertz band.The fourth kind of metamaterial based on VO₂ designed in this paper is a multi-layer perfect absorption metamaterial.Absorption of this metamaterial will change with the change of VO₂ conductivity.When the conductivity is 2000?^-1cm^-1,the absorption can be perfectly absorbed at 0.82THz.Therefore,the VO₂ material can be used to control the perfect absorption of this kind of metamaterial.The reflectivity and transmittance of this metamaterial change significantly with VO₂ conductivity,and VO₂ can be used to modulate all scattering parameters of Au/VO₂ multi-layer perfect absorbing terahertz metamaterials.The fabrication of VO₂ is the basis of the fabrication of the mentioned four kinds of metamaterials.Therefore,one of the key poing of experimental part of this article focuses on the process of VO₂ fabrication.According to the experimental conditions of our research group,the fabrication of the fourth kind of metamaterial is relatively easy to implement.Therefore,another focus of the experimental part of this paper is the fabrication of the fourth kind of metamaterial.