Abstract

We present techniques to generate multiple vortex with different topological charge by means of diffractive optical elements. Analytical formulae to describe the Fresnel and Fraunhofer diffraction of the Gaussian beam by a helical axicon (HA) are introduced. The relations are presented as a series of the hypergeometric functions. By setting the axicon parameter equal to zero, the solution for the HA changes to that for the spiral phase plate (SPP). The performance of the aforesaid optical elements is tested both through computer simulation and by experiments using a spatial light modulator, in view of optical miroparticle manipulation.