Visible and NIR transparent broadband microwave absorption metamaterial based on silver nanowires

In this study, a visible and near infrared (NIR) transparent and broadband microwave metamaterials absorber based on resistive silver nanowires (AgNW) films is designed and fabricated. The metamaterial unit consists of a concentric annular resonant pattern, a continuous conductive AgNW film and a transparent polymer frame. By using different types of support frames, the absorber can switch between rigidity and flexibility. The absorber has over 90% broadband microwave absorption from 4.1 to 18.2 GHz with 75% visible transparency and 66% NIR transparency. The absorber is polarization insensitive and can keep efficient absorption of TM or TE waves with an oblique incidence angle less than 30°. The radar cross section (RCS) of the absorber is reduced to more than 10 dB, covering all reflection angles and matching the absorption bandwidth range. Compared with traditional transparent microwave absorber (TMA) with indium tin oxide (ITO), the TMA in this work, specifically with high transparent in NIR has a great application in transparent electromagnetic windows of near infrared hyperspectral sensors and optical/laser seekers.