Generation of double-ring-shaped cylindrical vector beams by modulating Pancharatnam-Berry phase

In this work, we propose a method for generating double-ring-shaped cylindrical vector beams by modulating Pancharatnam-Berry phase (PBP). The theoretical analysis shows that the output field can be expressed as the coherent superposition of two circularly polarized Laguerre-Gaussian components with opposite polarization handness and opposite helical index when a linearly polarized fundamental Gaussian beam inputs the metasurface designed based on PBP. Such a superposition of Laguerre-Gaussian modes forms a double-ring-shaped cylindrical vector beam. Additionally, the local polarization orientation can be manipulated by changing the polarization angle of the input field. Our experimental results agree well with the theoretical expectation. We believe that PBP provides an extra choice to manipulate the phase and polarization of optical field.