Experimental and simulated verification of a frequency and amplitude tunable metamaterial absorber

In this paper, a dual band absorption characteristic of metamaterial absorber with three dielectric layers (SU-8 layer, VO₂ layer, Al₂O₃ layer) is proposed and experimental confirmed in terahertz region. These absorption peaks are originated from cavity resonance and electrical resonance, respectively. Impedance matching phenomenon between the proposed metamaterial absorber and free space is achieved at resonance frequencies of absorption peaks. In order to reveal the effect of geometrical parameters on absorption peaks, two groups of experiments are carried out. It is found that the cavity and electrical resonance absorption peaks show a shifted to higher frequency with the radius of holes array increasing. However, for the increase in the VO₂ layer thickness, the cavity and electrical resonance absorption peaks show a shifted to lower frequency. Absorption property is improved through optimizing structural parameters at room temperature condition. Moreover, measured results demonstrate that the cavity and electrical resonance absorption peaks show a shifted to higher frequency with the temperature increasing. Absorption intensities are tuned from 81% (25 °C) to 51% (97 °C) and 83% (25 °C) to 52% (97 °C), respectively. A new low-frequency absorption peak is achieved because that a new electrical resonance mode is effectively excited between the VO₂ layer and bottom metal layer. The proposed metamaterial absorber with tunable property shows the applications possibility in sensing and detecting based on external stimulus (such as heat, or light) leading to the absorption spectrum change. (paper)