The Research On The Design Of Fractional Micro-Optical Elements

Micro-optical elements become more and more widely used in modern science and technology because of their merits in high diffractive efficiency, small dimension, low weight, mass reproducibility and various optical functions. In order to extend its operation domain and improve the performance as well as the flexibility for geometry of an optical system, we propose a new algorithm, FrPI, to design micro-optical elements in fractional Fourier domain in which it can simultaneously optimizes the information of the space and the frequency domain. By inversely designing the initial phase for further iteration, the algorithm is fast, flexible and universal and can become a convenient tool for the design in fractional Fourier domain.For the requirement of various secondary optical sources in off-axis illumination system, we studied on the extension of beam shaping from the Fourier domain to fractional Fourier domain. By the design and simulation, we conclude that the fractional-Fourier-domain micro-optical elements can be conveniently applied in the off-axis illumination system for better result in beam shaping.We also propose a scheme to design diffractive optical elements for beam coherent combination in near field. The design method in fractional Fourier domain increases the degree of freedom by introducing the fractional order. Therefore it can improve the efficiency of beam combination and decrease the volume of the optical system.The simulation shows that the diffractive efficiency of designed elements is greater than 90% and the shaped results are better than that in Fourier domain.