Unidirectional Absorption in a Three-Dimensional Tunable Absorber Under Oblique Incidence

In this paper, we propose a three-dimensional tunable absorber to realize a controllable unidirectional absorption and unidirectional transmission based on the plasma metamaterial, which includes two metamaterial layers that are vertical to each other. Each side of the proposed absorber integrates two split-ring resonators, which are made in the solid-state plasma (SSP). Unidirectional absorption and unidirectional transmission can be achieved when the incident angle of the electromagnetic wave is 30 degrees. Furthermore, the unidirectional absorption and unidirectional transmission can be manipulated through exciting the different SSP resonators and adjusting the positions of the corresponding gaps between the two SSP resonators. In addition, the tunable absorption and transmission spectra can be obtained when the different SSP resonators are excited.