Wideband THz metamaterial absorber based on unpatterned resistive-sheet and water layers

A metamaterial absorber (MA) based on unpatterned resistive-sheet and water layers is proposed. It can provide wideband absorption with the absorptivity over 90% from 162 GHz to 1.5 THz and the relative bandwidth is high up to 161%. The anti-parallel surface currents between the layers of resistive-sheet and ground metal produce magnetic resonance, which contributes to a portion of the absorption. It is found that the water layer plays a leading role in the broadband strong absorption and the main power loss is concentrated in the water layer, which is mainly attributed to magnetic resonance at the border between water layer and PDMS layer. In addition, the absorber has polarization insensitivity and good stability at wide incident angles. The design of the proposed absorber is validated by the consistency between the simulated and calculated results. This work may provide a simple and time-saving approach to design wideband MAs.