Geometric-phase metasurfaces, recently utilized for controlling wavefronts of circular polarized (CP) electromagnetic waves, are drastically limited to the cross-polarization modality. Combining geometric with propagation phase allows to further control the co-polarized output channel, nevertheless addressing only similar functionality on both co-polarized outputs for the two different CP incident beams. Here we introduce the concept of chirality-assisted phase as a degree of freedom, which could decouple the two co-polarized outputs, and thus be an alternative solution for designing arbitrary modulated-phase metasurfaces with distinct wavefront manipulation in all four CP output channels. Two metasurfaces are demonstrated with four arbitrary refraction wavefronts, and orbital angular momentum modes with four independent topological charge, showcasing complete and independent manipulation of all possible CP channels in transmission. This additional phase addressing mechanism will lead to new components, ranging from broadband achromatic devices to the multiplexing of wavefronts for application in reconfigurable-beam antenna and wireless communication systems.

Geometric metasurfaces primarily follow the physical mechanism of Pancharatnam–Berry (PB) phases, empowering wavefront control of cross‐polarized reflective/transmissive light components. However, inherently accompanying the cross‐polarized components, the copolarized output components have not been attempted in parallel in existing works. Here, a general method is proposed to construct phase‐modulated metasurfaces for implementing functionalities separately in co‐ and cross‐polarized output fields under circularly polarized (CP) incidence, which is impossible to achieve with solely a geometric phase. By introducing a propagation phase as an additional degree of freedom, the electromagnetic (EM) energy carried by co‐ and cross‐polarized transmitted fields can be fully phase‐modulated with independent wavefronts. Under one CP incidence, a metasurface for separate functionalities with controllable energy repartition is verified by simulations and proof‐of‐principle microwave experiments. A variety of applications can be readily expected in spin‐selective optics, spin‐Hall metasurfaces, and multitasked metasurfaces operating in both reflective and transmissive modes.

In this paper, ultra-thin metalenses are proposed to generate converging and non-diffractive vortex beam carrying orbital angular momentum (OAM) in microwave region. Phase changes are introduced to the transmission cross-polarized wave by tailoring spatial orientation of Pancharatnam-Berry phase unit cell. Based on the superposition of phase profile of spiral phase plate and that of a converging lens or an axicon, vortex beam carrying OAM mode generated by the metalens can also exhibit characteristics of a focusing beam or a Bessel beam. Measured field intensities and phase distributions at microwave frequencies verify the theoretical design procedure. The proposed method provides an efficient approach to control the radius of vortex beam carrying OAM mode in microwave wireless applications for medium-short range distance.

Traditional methods of generating vortex beams based on metasurfaces consist mainly in modulating propagation phase or geometric phase. Here, by introducing detour phase, we propose the construction of dual-polarized vortex beam generators in the form of metasurface and metagrating (MG). The phase is modulated through moving the position of meta-atoms instead of varying the geometrical parameters or rotating the unit cells. To use detour phase, two kinds of unit cells are designed to achieve specific diffraction order. Each unit can arbitrarily and independently adjust the operation frequency and diffraction angle of transverse electric (TE) and transverse magnetic (TM) polarizations. Two vortex beam generators are designed and fabricated with different topological charges carried by orthogonal polarizations. To demonstrate the ability to independently manipulate, two polarizations of the generator based on MG are designed in different frequency bands. Both the simulation and experimental results validate the proposed method, showing great potential for polarization division multiplexing in orbital angular momentum (OAM) communication systems.