Active electromagnetic absorption metasurface with a switchable reflection band

An active electromagnetic (EM) absorption metasurface is proposed to achieve a switchable reflection band between two absorption bands. The metasurface consists of one lossy layer and one active layer separated by an air gap. The top lossy layer is composed of periodic metallic unit cells, designed to absorb the incident EM wave at the lower and higher absorption bands. PIN diodes are embedded on the bottom periodic array to control the reflection coefficient. When the PIN diodes are turned off, the incident EM wave is absorbed at lower and higher bands while reflected at the intermediate band; when the PIN diodes are turned on, the reflection band is switched off and a wide absorption band is achieved. Experimental results verify the numerical simulations.