Spin-controlled compact metalens based on the integration of Pancharatnam-Berry phase and Fresnel zone plate

Abstract By integrating Fresnel zone plates (FZP) with Pancharatnam–Berry (PB) phases, spin-controlled compact metalenses for multidimensional focusing are demonstrated. The position of the focal point can be modulated transversally and longitudinally by changing the PB phase profiles encoded into the FZP and adjusting the spin state of the incident circularly polarized (CP) waves. Concretely, combining an amplitude-type FZP (AFZP) with linear PB phase or spherical phase creates two focal points with orthogonal spin states in the transversal or longitudinal direction. On the other hand, for the phase-type FZP (PFZP), only single focus can be generated and manipulated due to the pure PB phase modulation. Moreover, multifocus modulation along the transversal or longitudinal direction can be achieved by encoding two kinds of PB phases into PFZP. This spin-controlled compact metalens combining the traditional FZP and recent metasurfaces offers a flexible approach for designing spin-controlled metadevices, with potential applications in multifunctional imaging and optical data processing.