Broadband thermal tunable infrared absorber based on the coupling between standing wave and magnetic resonance

In this paper, a simple thermal tunable metamaterial absorber with broadband absorption in the mid-infrared regime is designed and fabricated. The TiN/VO2/Al2O3/Al four-layer structure (with top Al circular patch arrays) introduces a specific dual-dielectric method to manipulate the coupling between standing wave and magnetic resonance for the metal-insulator-metal sandwich absorber. After structural optimization, the 80% absorption bandwidth reaches 2.9 μm in both simulation and experimental results. By virtue of the insulator-to-metal transition (IMT) of VO2, the reflectance increases from 5% to 42% by heating up the absorber from room temperature to 358 K leading to a relative stable radiation temperature at the crucial IMT stage (323~348 K). This design method is quite useful for active IR absorption (or camouflage) as well as thermal tuning.