Programmable graphene metasurface for terahertz propagation control based on electromagnetically induced transparency

Metasurfaces with programmable functions possess great potential in developing propagation control devices for electromagnetic waves. However, in the terahertz (THz) regime, most related metasurfaces are mainly focused on strength tuning and dual-function switching, otherwise relatively complex working conditions are required and the available controlling degree of freedom over the THz field is limited. Here, we propose a programmable graphene metasurface based on the quantum effect analogue, electromagnetically induced transparency. By varying the bias voltages applied to the graphene patterns connected to the dark resonators, the amplitude and phase of the unit cell's cross-polarized transmission can be continuously tuned and robustly switched between 0 and π, respectively. Based on this, flexible manipulations over the diffraction angles and focal lengths of the transmitted THz beams are achieved in either an amplitude or phase control manner. The proposed programmable scheme may provide new inspirations for designing THz programmable metasurface devices.