Construction of 3-D Microwave Helical Beams Using Huygens’ Metasurface

We propose a method for directly constructing three-dimensional (3-D) accelerating beams with twisted wavefront amplitude and phase profiles in real space. The design strategy combines the optical caustic method with antenna array theory to synthesize the required phase distribution over the transmitting aperture. The constructed beam is further enhanced by translating and superimposing the desired beam trajectory. The dynamics of the resulting helical beam are analyzed using Fresnel diffraction theory through a fast Fourier transform (FFT), revealing the uniform clustering of localized electromagnetic waves along the predefined curved trajectory in free space. Moreover, we demonstrate the generation of an antisymmetric double helical beam with distinct amplitude and phase characteristics. As an implementation example, we design a high transmittance (−0.9 dB) large-aperture Huygens’ metasurface (HMS) comprising 2307 miniaturized elements ( $0.37\lambda$ ) on a single-layer ultrathin ( $0.02\lambda$ ) dielectric substrate. Full-wave simulations are conducted to validate the feasibility of our design concept. This approach offers potential applications in near-field scenarios, including microwave power transmission, imaging, and biomedical fields.