Transparent and electrically tunable electromagnetic wave absorbing metamaterial

Electromagnetic protection materials are widely used in both military and civilian fields. However, the limited wave-absorbing band and low transparency of conventional electromagnetic protection materials are the impediment for extensive applications. Here, a transparent and electrically tunable wave-absorbing metamaterial for stealth technology and electromagnetic protection has been theoretically and experimentally realized. The trend of the absorption feature change in simulation is consistent with that of the experiment results. The main part of this material adopts a sandwich structure consisting of two layers of indium tin oxide (ITO) and one layer of glass in between. The upper ITO layer is periodically patterned and combined with varactor diodes, which function as a frequency-selective surface. The effective operating frequency range is in the S-band, which covers the common frequency band of WiFi and many other electronic devices. The wave absorbing performance of this material can be electronically tunable by changing the applied voltage. The main absorption peak can be up to 90% with a tunable amplitude range of 30% and a tunable frequency band range of 1 GHz, and the transmittance of the sample in the visible is 80.23%. The metamaterial has high performance on electromagnetic shielding, whose effectiveness is larger than 30 dB in the range of 2.6-3.95 GHz. This transparent and tunable metamaterial has great potential for the applications in electromagnetic protection and stealth.