Non-diffracted Airy beams based on multi-layer transmissive metasurface

Abstract

As a special beam with non-diffraction, self-bending and self-repairing characteristics, the traditional generation of Airy beam mainly relies on complex optical Fourier transform systems or liquid crystal spatial light modulators, which have problems such as large system size, high cost and difficulty in integration. Metasurface has become a new carrier for generating Airy beams due to its flexible control ability of electromagnetic waves with its subwavelength scale unit structure. This paper innovatively proposes a three-layer metal resonant ring metasurface, which realizes independent control of the amplitude and phase of the Airy beam, and successfully generates three types of non-diffraction Airy beams (one-dimensional, two-dimensional and annular self-focusing type), providing a new idea for efficient and compact Airy beam generation. The three-layer open metal ring unit structure designed in this paper optimizes the unit geometric parameters (such as ring radius, opening width and rotation angle), and uses the finite difference time domain (FDTD) method to simulate and verify the decoupling control ability of the unit at 8 GHz. On this basis, by arraying the amplitude and phase distribution of the encoded Airy function, the simulation results show that one-dimensional Airy beam, annular self-focusing Airy beam, and two-dimensional Airy beam exhibit excellent non-diffraction characteristics and have self-repair capabilities, while verifying the feasibility of multi-dimensional regulation. In terms of experiments, a two-dimensional Airy beam metasurface sample was made based on printed circuit board (PCB) technology, and its performance was verified in a microwave test system. The experimentally measured lateral light intensity distribution at different propagation distances is consistent with the simulation, confirming the feasibility of the design. In addition, the metasurface can still generate high-quality Airy beams in the 7.8–8.2 GHz frequency band, showing good broadband adaptability. The designed three-layer resonant ring metasurface overcomes the limitations of traditional Airy beam generation methods and contributes to the precise application of Airy beams in the microwave field.