Generation of nonuniform vortices based on metasurfaces and their feature characterization

In view of the wide applications of vortices and the inevitable occurrence of nonuniform vortex in practice, the generation of nonuniform vortices and their feature characterization are proposed. Nonuniform vortices are different from uniform vortices, and their helical phase does not change uniformly with the azimuthal angle. The possible models of nonuniform vortices including several cases with nonlinear phase in equal intervals, linear phase in unequal intervals, and nonlinear phase in unequal intervals are proposed. The feature characterization for the phase and intensity distributions of nonuniform vortices are performed using the forked fringes and the far-diffraction of forked fringes. These nonuniform vortices are also produced with the help of vortex metalenses consisting of rotated nanoholes. The study about the nonuniform vortices is helpful for understanding and estimating practical vortices.