Efficient generation of a perfect optical vortex by using a phase optical element

We consider generation of a perfect optical vortex by three elements: (i) amplitude-phase element with its transmission being proportional to the Bessel function, (ii) optimal element with the transmission proportional to the sign of the Bessel function, and (3) helical axicon. Maximal intensity of light on the ring is shown to be achieved by using the optimal element. Thickness of the light ring generated by the axicon is approximately two times higher than that for other elements. For perfect optical vortices with the radius of several wavelengths we detect the range of topological charges, within which the ring radius is almost independent on them.