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The electromagnetic scattering of an object is directly related to its physical geometry and material properties. While metasurfaces show excellent performances in mimicking material properties almost at well by flexibly designing meta‐atoms with arbitrary electromagnetic responses, their physical geometries are generally in a regular manner. The break of a metasurface's geometry will inevitably affect its electromagnetic scattering that introduces uncertainty in wavefront manipulation. Here, a general approach for highly efficient wavefront manipulation with irregular shaped metasurfaces is proposed. Such an approach establishes a universal iterative modulation relation between the metasurface and scattered field by introducing boundary constraints at the aperture, enabling to deal with the electromagnetic scattering from a metasurface with arbitrary spatial shape. In this way, the desired wavefront form can be engineered using meta‐atom sequences with arbitrarily shaped aperture. As a proof of concept, a flower‐shaped metasurface operating in the reflection mode is designed and experimentally demonstrated for reconstructing four random focuses with uniform and high‐efficiency intensity distribution at near‐field region, while the flower shaped field pattern can be extracted near the aperture plane. Such a method may pave a new route for advanced wavefront manipulation and electromagnetic concealment/camouflage applications.

The recent advent of digital coding metasurfaces notably simplifies the design of functional devices, enabling one to manipulate electromagnetic waves in exotic ways using specifically arranged coding elements representing discrete phase states. Here, we propose a design of dielectric coding metasurface with diverse functionalities, which are achieved by encoding the metasurface unit cells with different coding sequences. As proofs of concept, we demonstrate the possibility of realizing five distinct functionalities for the normal incidence of plane microwaves: anomalous reflection, multibeam generation, diffuse scattering, beam focusing, and vortex beam generation. The near-field distributions and far-field scattering patterns are obtained by full-wave numerical simulations to analyze the behavior of the waves in each of the cases and illustrate our general theoretical predictions.

Metasurfaces, a kind of two-dimensional artificially engineered surfaces consist of subwavelength unit cells, have recently attracted tremendous attention, owing to their exotic abilities for tailoring electromagnetic responses. With active lump elements incorporated into the design of metasurfaces, dynamic reconfigurabilities enabled by external stimuli could be realized, offering opportunities for the dynamic manipulation of electromagnetic waves. In this mini review, we present a brief review on the recent progress of electrically reconfigurable metasurfaces at microwave frequencies. A brief discussion will also be given with our outlook on future development direction and possible challenges in this interesting field.

offer high degree of holographic data capacity and state-of-theart visual image encryption. However, in all these works, each valid information corresponds to one individual decryption key in each channel, so that the difficulty of information deciphering can be improved only by increasing the diversity of the electromagnetic channels. In addition, the information leakage of any one of the channels may cause the eavesdropper to decipher all the relevant information directly.Based on the Moire effect from random dots, human visual system (HVS) can be used to identify the local correlation from random noise grids and combine them from different regions of the visual field. [25] This characteristic of HVS was later extended for images encryption by encoding the secret information into several noiselike random grids. [26] As these random grids are stacked and viewed together, the secret information can be emerged from the random background noise. Visual secret sharing (VSS), also named as visual cryptography, [27][28][29][30][31] as the derivative of this mechanism, describes an effective encryption strategy where the secret information can be encoded to n mutually-unrelated shared keys (SKs) and distributed to n participants so that any k ðk ≤ nÞ of n combinations of the authorized participants can recover the secret information, while any less than k participants reveal nothing of the secret. Obviously, the VSS established a well-recognized simple and secure method for information protection, which has been adopted in