and holographic plates. [12,13] Nevertheless, most of aforementioned metasurfaces are composed of passive metaparticles and generally behave one EM functionality, which cannot satisfy the largely increasing demand of multifunctional devices. Although several substantial efforts have been devoted to combine the multiple EM functionalities into one single metasurface, the realized multifunctionalities can only be acquired at different polarization states or frequencies. [14][15][16][17][18] More recently, much more attention has been focused on the design of reconfigurable metasurfaces by employing tunable metaparticles driven by thermal effect, [19,20] electrical tuning, [21,22] mechanically stretching, [23,24] and so on. The realistic possibility of reconfigurable metasurfaces has been demonstrated in optical, terahertz, and microwave regions, accompanied by the emergence of interesting applications, such as beam steering, [25,26] tunable absorbing, [27,28] chiral polarization switching, [29,30] and so on. The reconfigurability of metasurface in optical and terahertz domains is generally realized by exploiting the active medias, including graphene, [31] liquid crystal, [32] vanadium dioxide, [33] and Ge 2 Sb 2 Te 5 (GST). [34,35] In the microwave region, metasurfaces achieve the tunable EM responses through the general method of integrating discrete elements such as varactor diodes, [36,37] PIN diode switches, [38,39] and MEMS switches [40] within the metaparticles. In ref.[28], the metasurface with varactor diodes involved was proposed to tune the absorbing frequency. In ref.[38], the PIN diodes were adopted to design the polarization-reconfigurable metasurface that can dynamically control the handedness of the circularly polarized wave. The above lumped components have also been used to achieve the dynamical control of EM wavefront. [40] However, most of the realized tunable metasurface focused on the reconfiguration of a single one function (e.g., absorbing frequency, polarization feature, and beam deflection angle). The latest efforts started to be devoted to the design of multifunctional metasurface that integrates diversified functionalities into a monolayer metastructure. [39,41] In ref.[39], microelectromechanical system (MEMS) technology was utilized to construct the metasurface with tunable resonance for obtaining 360° phase span, and based on the phase modulation, the multifunctionalities, including polarization control, wavefront deflection and holograms, have been numerically demonstrated. In ref.[41], a programmable metasurface was reported Metasurfaces provide a novel strategy to manipulate electromagnetic (EM) waves by controlling the local phase of subwavelength artificial structures within the wavelength scale. So far, many exciting devices have been developed and most of them are based on passive metasurface, which can only perform a specific functionality. It is still very challenging to simultaneously achieve multiple EM functionalities and real-time reconfigurability in one design. This stud...

Recently, a concept of digital metamaterials has been proposed to manipulate field distribution through proper spatial mixtures of digital metamaterial bits. Here, we present a design of 2-bit digitally-controlled coding metasurface that can effectively modulate the scattered electromagnetic wave and realize different far-field beams. Each meta-atom of this metasurface integrates two pin diodes, and by tuning their operating states, the metasurface has four phase responses of 0, π/2, π, and 3π/2, corresponding to four basic digital elements “00”, “01”, “10”, and “11”, respectively. By designing the coding sequence of the above digital element array, the reflected beam can be arbitrarily controlled. The proposed 2-bit digital metasurface has been demonstrated to possess capability of achieving beam deflection, multi-beam and beam diffusion, and the dynamical switching of these different scattering patterns is completed by a programmable electric source.

space was proposed on this background. Different from the full-cloaking technique, the carpet cloak hides objects under a ground plane, and any object covered by the carpet cloak appears as a metallic flat plate. Nevertheless, this cloak is still bulky in size, which is usually comparable with the size of the hidden object. In addition, it will generally introduce a lateral shift of the scattered wave, making the objects detectable. [15] Recently, development of metasurfaces [16][17][18][19][20][21][22] further relaxes the limitations of cloaks based on bulk metamaterials, providing a novel route to design a more practical carpet cloak. Metasurface, as a 2D