Abstract
In the diffraction image formed by a diffractive optical element with a coherent laser beam, optical vortices appear. Preventing optical vortices in a diffraction image is an important issue particulary in beam shaping application. In this letter, a novel design of diffractive optical elements for generating vortex-free diffraction images is proposed. It is manifested that the key point of preventing optical vortices is the apodization of the aperture of a diffractive optical element. The optimization of the aperture apodization process based on the genetic algorithm is discussed.