A Reconfigurable Graphene Reflectarray for Generation of Vortex THz Waves

A reconfigurable graphene reflectarray is proposed for the generation of vortex radio waves at THz. First, a simple sectored circular reflective surface model with a plane wave at normal incidence is constructed to illustrate how vortex radio waves can be generated. Then, a graphene reflective cell is examined to demonstrate that the reflection coefficient can be controlled by changing the chemical potential and size of the graphene patch. Next, the sectored circular reflective surface is realized with the graphene reflective cells that are properly sized, arranged, and biased to satisfy the required reflection coefficients for various modes of vortex radio waves. Finally, the graphene reflectarray is excited with a horn antenna, showing from simulations that it can be dynamically reconfigured to generate the 0, ±1, and ±2 modes of vortex radio waves at 1.6 THz.