Microwave-Vortex-Beam Generation Based on Spoof-Plasmon Ring Resonators

Abstract

Vortex beams carrying orbital angular momentum (OAM) have recently attracted great interest due to their capability for providing a new method to increase the communication channels in wireless communications. It is expected that the unbounded eigenstates of OAM can bring a large number of channels to enhance the transmission capacity. Here, we propose an effective strategy to generate vortex beams by using spoof surface plasmon polaritons (SSPPs) in the microwave region. A periodically modulated SSPP ring resonator is applied to convert near-field SSPP waves into radiating a vector vortex beam. The emitted beam can possess different OAM modes at different frequencies through rational design. In addition, circularly polarized vortex beams are demonstrated. Both numerical simulations and experimental characterizations confirm the theoretical predictions. Owing to the deep subwavelength characteristic of SSPP, the proposed device can be readily integrated into miniaturized circuits and systems. We anticipate that our design will enable a wide range of applications for future wireless communication technologies.