Generation of multiple vortex-cones by direct-phase modulation of annular aperture array.

The generation of multiple vortex cones using an annular aperture array and a spatial light modulator (SLM) is studied. The direct downscale imaging of an SLM on the surface of an annular aperture enables the direct-phase modulation of the annular aperture. It is experimentally demonstrated that the direct-phase modulation of an annular aperture array can control both the topological charge and the horizontal positions of multiple vortex cones simultaneously.