Analysis and Design of a Broadband Metasurface- Based Vortex Beam Generator

Metasurface-based vortex beam generators are very promising and applicable to enhance transmission data capacity in wireless communication system. However, most designs to date are ceased to predict their far-field characteristic, which is actually in demand when applied to wireless communication. Here, we find for the first time a deterministic and robust strategy to fastly estimate the exact far-field patterns and gain limit of a vortex beam based on the theoretical analysis of aperture field with spiral phase profile. For verification, a broadband metasurface-based vortex-beam generator based on geometric phase is designed, numerically calculated and experimentally measured at microwave regime. Excellent agreements are observed among far-field results obtained based on the proposed method, numerical simulations and experimental measurements, firmly demonstrating the validity and correctness of the proposed strategy. Such a deterministic and robust strategy of predicting far-field characteristics of a vortex beam may pave the way for its applications in many engineering scenarios, such as conical beam design, wireless communication, et al.