Design of Diffractive Optical Elements for Beam Shaping in Near Fresnel Diffraction Domain

Fast optimization algorithms of the design of diffractive optical elements (DOEs) for beam shaping are often based on fast Fourier transform (FFT), and the demand of the sampling theorem must be met when FFT is used to calculate the light intensity. Limited by the fabricating technology, the pixel size of a DOE cannot be too small. For beam shaping in Fresnel diffraction domain, given that the sampling interval of a DOE is fixed, if the diffraction distance is too short, all FFT algorithms would not meet the demand of the sampling theorem, and then the results of beam shaping would become worse. In this paper, the disadvantages of the FFT algorithms in near Fresnel diffraction domain are discussed, and an area division method is proposed for the DOEs design. The simulation and experimental results show the validity of the proposed area division method.