Perfect Control of Diffraction Patterns with Phase-Gradient Metasurfaces

Abstract

Phase-gradient metasurfaces (PGMs) constitute an efficient platform for deflection of a beam in a desired direction. According to the generalized Snell's law, the direction of the reflected/refracted wave can be tuned by the spatial phase function provided by the PGMs. However, most studies on PGM focus only on a single diffraction order, that is, the incident wave can be reflected or refracted to a single target direction. Even in the case of multiple beams pointing in different directions, the beams are still in the same order mode, and the energy carried by different beams cannot be controlled. In addition, the energy ratio of multiple beams is generally uncontrollable. Here, we propose a general method to perfectly control diffraction patterns based on a multi-beam PGM. An analytical solution for arbitrarily controlling diffraction beams is derived through which the generation and energy distribution in high-order diffraction beams can be achieved. Three metasurfaces with different diffraction orders and energy ratios are designed and fabricated to demonstrate the proposed method. The efficiencies of diffraction for the desired channels are close to 100%. The simulated and measured far-field patterns are in good agreement with theoretical predictions, validating the proposed method that provides a new way to design multi-beam antennas and that has significance in wireless communication applications.

Comparison of the Moist Material Relative Permittivity Readouts Using the Non-Invasive Reflectometric Sensors and Microwave Antenna

“…In order to implement this method in the real design, it seems necessary to develop a compact antenna with appropriate broad frequency bandwidth and high gain. For this purpose, it may be valuable to implement a kind of metamaterial technology, as shown in the exemplary references [ 81 , 82 ]. This approach would improve the performance of both microwave antennas and TDR sensors.…”

Spatial filtering magnetic metasurface for misalignment robustness enhancement in wireless power transfer applications

“…In this way, the electromagnetic waves impinging on metamaterials are myopic to their elementary lattice and they interpret them as homogeneous materials [10][11][12][13] . Their potentialities to show desirable electromagnetic properties from radio to optical frequencies have been proved to be extremely useful in several different applications, such as frequency-selective surfaces, electromagnetic absorbers, lenses, and biomedical applications [14][15][16][17][18] .…”

Multilevel Spiral Axicon for High-Order Bessel–Gauss Beams Generation

“…One solution for this is to use nondivergent OVs, called high-order Bessel–Gauss beams, which exhibit annihilation reconstruction properties and stability in atmospheric turbulences [ 5 , 8 ]. One can generate diffraction-free OVs with axicons [ 10 , 11 , 12 , 13 , 14 ], either by loading a high-order phase hologram on a spatial light modulator [ 15 , 16 , 17 ], amplitude binary masks [ 15 ], or shaping a Laguerre–Gauss beam with a refractive axicon—a doublet of a real spiral phase plate and a zero-order refractive axicon (with continuous profile) [ 18 ], Pancharatnam–Berry phase elements [ 18 ], a digital micromirrors device [ 19 ], circular Dammann gratings [ 20 ], Mach–Zehnder interferometer [ 21 ], cylindrical waveguides [ 22 ], conformal transformation elements (for OAM detection) [ 23 , 24 , 25 ], or metasurfaces [ 26 , 27 ].…”