Design of binary optics composite array element for inertial confinement fusion (ICF) target uniform illumination

Abstract

The research on Inertial Confinement Fusion (ICF) is very important in the field of Energy and National Defence. Rigorous requirements of target illumination are proposed in ICF experiments, such as flat top, steep edge, low sidelobes and high light efficiency. Such uniform illumination is also required in some other fields, for example, laser manufacturing. Using Binary Optical Elements to realize such uniform illumination has many advantages, such as high light efficiency owing to pure phase modulation, strong phase distribution design flexibility and so on. When ring laser input and conventional Binary Optical Element Array is adopted, the filling factor is only 63.7% and the light efficiency is very small. In this paper, to increase the filling factor and exploit the light energy sufficiently, a kind of binary optics composite array element, whose shape approximates to a circular by containing some series of square units with different sizes, is designed to realize the uniform illumination needed in ICF. This elements' filling factors are greater than 90% and their 2D light efficiencies are more than 83%. Two dimensions are converted to one dimension to simplify the design. Hybrid algorithm based on hill-climbing and simulated annealing is utilized for phase optimization. Simulated results show the validity of this kind of method.