Design of diffractive phase elements for beam shaping in the fractional Fourier transform domain

Based on the general theory of the amplitude-phase retrieval problem, we present a new approach for the design of diffractive phase elements (DPEs) to implement beam shaping in the fractional Fourier transform (FRFT) domain. We derive the unitarity transform condition for a FRFT system and find that for the given structural parameters of optical system, the nonunitarity of the discrete FRFT depends on its fractional order. Numerical simulations are carried out in designing the DPEs to convert a Gaussian-profile beam into a uniform-profile beam in 1D optical system and the rotationally symmetric optical system both, for different fractional orders and different parameters of beam. In all the cases studied, our algorithm provide an effective method in designing the DPEs that can implement the beam shaping with a high quality.

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