Generation of Periodic Nondiffractive Beams Along Straight and Curved Trajectories Based on 3-D-Printed Metasurface

Abstract

In this paper, two kinds of periodic nondiffractive beams along arbitrary trajectories, including non-accelerating and self-acceleration types, are generated by 3D-printed all-dielectric metasurfaces. The first step is to produce continuous non-accelerating and self-acceleration beams, i.e. Bessel beam and Bessel-like beams. By an appropriate modification of the conical ray pattern of the standard Bessel beams, self-accelerating Bessel-like beams can be realized. In the second step, by removing some expanding phase equivalent circles in a periodic fashion and binary modulating of the phase masks, the central main lobe of continuous beams can be modified into pulsating ones. In the third step, we construct real physical models based on the derived theories. All phase coverage can be achieved by changing the height of the proposed cube element. Therefore, the final phase distribution can be mapped to height information of each unit cell. For demonstration, several proof-of-principle metasurfaces are printed and measured, two of which are used to generate Bessel beams along different straight directions, and two of which are used to produce Bessel-like beams along C-shaped and S-shaped trajectories. In all cases, during propagation, the intensity peak alternately switches its position between the main lobe and the outing rings. Meanwhile, the measured trajectories are highly consistent with the predefined ones. The proposed metasurfaces are expected to be utilized in numerous applications like secure communication.