Orbital angular momentum beam antenna systems for wireless communications – a brief review

Orbital angular momentum (OAM) beams, also known as vortex beams, have gained a significant attraction in the past decade. Their ability to offer an infinite number of modes (theoretically) opens doors to develop new high data-rate and secure communication system. In this paper, we present the general theory of OAM beams and give a brief overview of different techniques presented in the literature to achieve such beams with high order mode purity.