Multifunctional metasurface coding for visible vortex beam generation, deflection and focusing.

Vortex beams, as beams carrying orbital angular momentum (OAM), exhibit unique donut-shaped intensity distributions and helical wavefronts. They are widely applied in fields such as optical communication, nanoparticle manipulation, and quantum information. Traditional vortex beam generation methods, such as those based on Pancharatnam-Berry phase design, can effectively generate vortex beams, but the conversion efficiency and design flexibility are limited by polarization states and incident angles. In addition, the generated and propagated vortex beams require separate metasurface for wavefront deflection and refocusing for practical applications. This work proposes a novel metasurface design approach based on resonant phase, where phase coverage of 2 is achieved by varying the radius of the nanocylinders. In addition to the efficient vortex beam generation in the visible regime, we have tackled the challenge of simultaneous control of vortex beam's anomalous deflection and refocusing, through different encoding sequences superimposed based on the principle of Fourier convolution and metalens design. This all-in-one multifunctional metasurface design offers new technological pathways for secure optical communication and quantum manipulation applications.