Abstract
A new broadband tunable metamaterial absorber based on different radii of vanadium dioxide (${\rm VO}_2$) rings loaded on the dielectric layer is designed. According to the insulator-to-metal phase transition characteristics of ${\rm VO}_2$ under thermal excitation, the dynamic adjustment of the absorption by the external temperature is achieved. The simulation results demonstrate that when ${\rm VO}_2$ is in its metal phase at high temperature, an absorption greater than 90% in the bandwidth range of 2.64–7 THz can be obtained and its relative bandwidth is reached to 90.5%. However, the absorption rate in the same frequency range is always lower than 2.3% when ${\rm VO}_2$ is in the insulator phase at low temperature, which means that the absorber can be used as a perfect reflector. The maximum tunable range of the proposed absorber can be realized from below 2.3% to nearly 100%. We further analyze and discuss the equivalent impedance and electric field distribution of the absorber and clarify the adjustment mechanism of the absorption performance of the ${\rm VO}_2$ ring. In addition, a multireflection interference theory is also investigated to quantitatively explain the physical absorption mechanism. Such a tunable broadband absorber based on temperature control has great potential to be applied to sensors, thermophotovoltaics, and wireless communication.
© 2020 Optical Society of America
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