Features of the Optical Vortices Diffraction on Silicon Ring Gratings

We study the diffraction of optical vortices on silicon ring gratings and diffractive axicons with a change in the relief height of optical elements in this paper. It was shown that for silicon ring gratings with variable height it is possible to obtain a light focal needle 83.8% longer than the light needle formed by a standard diffractive axicon. The increasing of the diffractive axicon height reduces the size of the focal spot by 24% compared to an axicon with a standard height.