Generation of High-Efficiency Vortex Beam Carrying OAM Mode Based on Miniaturized Element Frequency Selective Surfaces

In this paper, a new method for generating high-efficiency vortex beam carrying orbital angular momentum (OAM) mode is proposed based on the miniaturized element frequency selective surfaces (MEFSS) in the microwave region. The unit cell is a class of sub-wavelength periodic structure, which is composed of non-resonant elements with a low profile. A flat metalens is designed to control the wavefront of the propagating electromagnetic waves based on different phase responses of eight kinds of MEFSS unit cells. Under linearly-polarized normal incidence, a vortex beam carrying OAM mode with a topological charge of 1 is excited. The measurement results are in good agreement with the theoretical prediction and full-wave simulation. The proposed method shows great potential applications in generating OAM mode with high efficiency at microwave frequencies.