Abstract
Abstract Controlling spin electromagnetic waves by ultra-thin Pancharatnam-Berry (PB) metasurfaces show promising prospects in the optical and wireless communications. One of the major challenge is to precisely control over the complex wavefronts and spatial power intensity characteristics without relying on massive algorithm optimizations, which requires independent amplitude and phase tuning. However, traditional PB phase can only provide phase control. Here, by introducing the interference of dual geometric phases, we propose a metasurface that can provide arbitrary amplitude and phase manipulations on meta-atom level for spin waves, achieving direct routing of multi-beams with desired intensity distribution. As the experimental demonstration, we design two microwave metasurfaces for respectively controlling the far-field and near-field multi-beam generations with desired spatial scatterings and power allocations, achieving full control of both sophisticated wavefronts and their energy distribution. This approach to directly generate editable spatial beam intensity with tailored wavefront may pave a way to design advanced meta-devices that can be potentially used in many real-world applications, such as multifunctional, multiple-input multiple-output and high-quality imaging devices.
Highlights
As the two-dimensional (2D) equivalence of metamaterials, metasurfaces have shown unprecedented abilities to manipulate the electromagnetic (EM) waves within sub-wavelength thickness that is far beyond what can be achieved by naturally occurring materials
We design two microwave metasurfaces for respectively controlling the farfield and near-field multi-beam generations with desired spatial scatterings and power allocations, achieving full control of both sophisticated wavefronts and their energy distribution. This approach to directly generate editable spatial beam intensity with tailored wavefront may pave a way to design advanced meta-devices that can be potentially used in many real-world applications, such as multifunctional, multiple-input multiple-output and highquality imaging devices
To give the experimental verifications, we propose two functional devices for directly routing the far-field and near-field EM behaviors in microwave region: the first metasurface can simultaneously control the propagation directions of multiple beams and the power allocation of each scattered beam; the second bi-foci metasurface can achieve independent control of the position and power of each focal spot
Summary
As the two-dimensional (2D) equivalence of metamaterials, metasurfaces have shown unprecedented abilities to manipulate the electromagnetic (EM) waves within sub-wavelength thickness that is far beyond what can be achieved by naturally occurring materials. This limitation can be somehow resolved so that the objective of simultaneously control over the beam propagation direction and power intensity allocation is achieved [20] This method consumes large computing resource and time. G., ultra-low side-lobes or reduced speckle in hologram [21,22,23,24,25], can be directly achieved through theoretical formulas, without resorting to the complex and time-consuming optimizations Due to these merits, the amplitude-phase modulation metasurfaces insure a wide range of applications such as high quality holography, synthesis of complex wave fields, and so on [21, 22]. The two prototypes are fabricated and measured, which validates the good performances of our proposals
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