Design and Analysis of Binary Fan-out Gratings based on Step-Transition Perturbation Approach

摘要

Nowadays, diffractive optical elements are used for a variety of applications because of their high design exibility,compact size, and mass productivity. At the same time, they require having high and complex opticalfunctionalities such as a large number of diffraction orders and a wide diffraction angle, which is beyond thelimits of scalar paraxial diffraction domain. We propose a stable and fast gradient-based optimization algorithmbased on step-transition perturbation approach applied to design binary diffractive elements with small andmany features for being performed in a large number of diffraction orders and wide diffraction angles. Using ouroptimization, we obtained high-performance elements than using optimization based on purely scalar theory. Inaddition, it needs much less calculation time than parametric optimization based on rigorous diffraction theory.Upon verification with the experimental results, we observed that our gradient-based optimization method isvalid for 1-by-117 fan-out grating with some small features (on the order of the illumination wavelength) andabout 22° full pattern diffraction angle.