Novel ultrathin dual-functional metalenses are proposed, fabricated, tested, and verified in the microwave regime for the first time. The significance is that their anomalous transmission efficiency almost reaches the theoretical limit of 25%, showing a remarkable improvement compared with earlier ultrathin metasurface designs with less than 5% coupling efficiency. The planar metalens proposed empowers significant reduction in thickness, versatile focusing behavior, and high transmission efficiency simultaneously.

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.