Vortex beam generation using circular leaky-wave antenna

Vortex beams, which are electromagnetic beams carrying orbital angular momentum, have a great potential for communication, sensing, imaging and tweezing applications. Unfortunately, the spatial light modulator technology that is used in the optical regime to generate vortex beams is not applicable at radio frequencies and the recently introduced metasurface technology suffers from integration difficulty. To solve these issues, we introduce here the concept of generating vortex beams using a circular leaky-wave antenna (CLWA). In this approach, the spiral-shaped phase fronts of the vortex wave are produced by the interference of circularly twisted phase fronts due to off-broadside radiation in the unfolded antenna, while the beam is obtained from the restricted circular aperture of the CLWA. The paper explains the principle in details and provides an experimental demonstration for the case of unit topological charges. The antenna may support simultaneously different orbital angular momenta so as to provide an unprecedented multiplexing technology.