This thesis describes the design, fabrication and characterization steps for beam shaping diffractive optical elements (DOEs). The elements aim at reshaping a Gaussian intensity profile to a circular and square top-hat intensity profile. A top-hat intensity profile can be interesting for industrial applications where high uniform intensity profiles and sharp edges of the profile are needed, like 3D printing or high accurate laser cutting. The design of the DOEs was done with the help of the VirtualLab simulation software which uses an iterative Fourier transform algorithm to find the best phase profile of the elements. The different aspects of the design and optimization process are explained. The DOEs were fabricated by a two-photon polymerization-based 3D printing process. The software DeScribe will be introduced, which generates the files that describe how the design needs to be printed. The presence of dirt particles and defects on the printed DOEs was checked with an optical microscope. The height profile of the elements was measured with a non-contact profilometer which allowed to check if the DOEs were printed correctly. The measured output fields are presented and possible causes for irregularities in the output field are also presented.