Polarization-independent adjustable broadband terahertz metamaterial absorber based on vanadium dioxide rings

Abstract

The emergence of polarization insensitive and adjustable terahertz metamaterial absorbers promotes the wide application of terahertz technology. In this paper, an adjustable broadband absorber based on vanadium dioxide (VO₂) is designed. The device adopts a simple sandwich structure: the bottom layer is gold, the medium is quartz, and the top layer consists of three VO₂ rings with gaps. The plasmon resonance generated by the top layer pattern and the coupling effect between the rings jointly lead to the emergence of the broadband absorption spectrum. The absorptivity exceeds 90% within the frequency range of 2.81–7.71 THz, with a bandwidth of 4.9 THz and a relative bandwidth of 93.16%. By varying the thickness of the VO₂ ring and the width of the gaps, the absorptivity can be higher than 95% between 3.17 and 7.50 THz, providing an additional option for industrial applications. Additionally, the proposed absorber is polarization-insensitive, incident stable and has high parametric fault tolerance. When the conductivity of VO₂ changes from $2\times 10^2$ to $2\times 10^5$ S/m, the absorptivity at 2.84 THz can continuously vary from 1.44% to 91.91%, and the modulation depth reaches 98.43%. These properties are beneficial for the preparation and application of absorbers. Furthermore, a model based on multiple interference theory is also utilized to verify the absorption spectra of the simulation model. This exploration offers a new alternative for switch, modulator, communication, and other applications.