Figure 1: (Colour online) scheme for a double-ring-shaped azimuthally polarized beam focused by a binary phase plate with high NA lens. The red arrows in (a) shows the direction of polarization. (b) is the DOE and is placed near the lens approximately the distance between lens and the source. The point in (c) represents the radial and axial coordinates of the observation point at the focal plane relative to the focus point, and is the azimuth angle defining the radial direction.