Over last two decades, metamaterials have gained considerable momentum and emerged as one of the most promising area of electromagnetics. [1,2] Metamaterials are composed of artificially periodic metallic or dielectric structures with subwavelength scale which enable us to achieve unique electromagnetic (EM) properties such as perfect absorption [3] and negative refraction. [4] Despite the success of metamaterials in fundamental physics, devising metamaterials for real applications still remains a big challenge due to their large volume and complex fabrication. Metasurfaces, the 2D equivalence of metamaterials with planar profile, serve as an alternative approach to bypass the volume

Reconfigurable metasurfaces have emerged as a versatile platform for reshaping the wireless environment into a desirable form at low cost. Despite the rapid growth, most of the existing metasurfaces only support reflection operation or transmission operation, only providing service coverage of backward or forward half-space when they are used for wireless communications. Here, an intelligent programmable omni-metasurface integrating reflection mode, transmission mode, and duplex mode of simultaneous reflection and transmission modes in the same polarization and frequency channel is proposed, capable of providing ubiquitous full-space service coverage for multiuser wireless communication applications. As exemplary demonstrations, a series of dynamic functionalities have been realized, including twin-beam scanning in reflection mode, twin-beam scanning in transmission mode, and identical/distinct dynamic beams for both forward and backward half-spaces in duplex mode, which are customized for signal reflection, transmission, and simultaneous symmetric/asymmetric reflection and transmission in wireless communication scenarios. The proposed tunable omni-metasurface provides a new method for full-space wave manipulation, which may offer untapped potentials for real-time, fast, and sophisticated wave control in applications such as miniaturized systems, integrated photonics, and intelligent communications.

Metasurface retroreflectors, which scatter the incident electromagnetic wave back to incoming direction, have received significant attention due to their compelling advantages of low profile and light weight compared with conventional bulky retroreflection devices. However, the current metasurface retroreflectors still have limitations in wide-angle and omnidirectional operations. This work proposes a high-efficiency, wide-angle, reconfigurable, and omnidirectional retroreflector composed of spin-locked phase gradient metasurface with a thickness of only 5.2 mm or 0.07 operating wavelength. The reflection phase of constituent meta-atoms can be controlled dynamically and continuously by altering their orientation states through individually addressing each mechanically rotational meta-atom, whereas the reflection handedness is kept the same as incidence. Therefore, adaptive and arbitrary momentum can be imparted to the incident wave, providing high-efficiency retroreflection over a wide continuous range from −47°to 47°. Moreover, such high-performance retroreflection is extended to omnidirectional level, enabling great degrees of freedom that are unavailable by previous researches. As a proof of concept, a retroreflective metasurface is fabricated and experimentally demonstrated at microwave frequencies. The proposed thin thickness, high efficiency, and reconfigurable metasurface retroreflector can be extended to other frequencies that may offer an untapped platform toward reconfigurable spin-based retroreflection devices for electromagnetic signal processing.

Kirigami technique, a method to reconfigure structures via mechanical approaches, has received much attention in material science, due to its versatile and unconventional structural transformations. The counterparts in the electromagnetic metamaterial field has recently allowed for the tunable control of electromagnetic responses. However, they are limited to global tuning of absorption, chirality, etc., leaving much potential of controlling spatially varying distribution and therefore the optical wavefront unexploited. Here, the authors propose a class of kirigami‐based reconfigurable gradient metasurfaces through which the electromagnetic wavefront can be tuned over continuous‐state ranges by changing the meta‐structures from folded (compact) to unfolded (large surface) configurations. As the proof‐of‐concept, meta‐devices including switchable anomalous refractor and reconfigurable metalens are demonstrated both in simulations and experiments. Moreover, a new paradigm to mitigate chromatic dispersion is also realized by the kirigami‐based reconfigurable metalens, which is able to keep the focal length unchanged over a continuous frequency band by setting metalens with various folding states. Their approach provides a new alternative for designing reconfigurable gradient metasurface with additional mechanical properties and may have potential applications in advanced devices such as reconfigurable optical components and imaging system.

Active metasurfaces with dynamically switchable functionalities are highly in demands in various practical applications. In this paper, we experimentally present an active metasurface based on PIN diodes which can realize nearly perfect reflection, transmission and absorption in a single design. Such switchable functionalities are accomplished by controlling the PIN diodes integrated in both layers of the metasurface. A transmission line model is employed to further investigate the underlying mechanism of the metasurface. This proposal is confirmed by numerical simulations and experiments. As a novel metasurface with multiple switchable functionalities, our design may find some practical applications such as smart radomes.