<title>Continuous-phase diffractive optical element to realize uniform target illumination in inertial confinement fusion (ICF)</title>

Abstract

Rigorous requirements of target illumination are requested in Inertial Confinement Fusion (ICF) experiments, such as flat top, steep edge, low sidelobes and high light efficiency. Using Diffractive Optical Elements (DOEs) to realize such uniform illumination has many advantages, such as high light efficiency of pure phase modulation, strong flexibility of phase design and so on. A kind of hybrid algorithm based on hill-climbing and simulated annealing is utilized for phase design because of the ability of strong convergence of the hill-climbing and the global optimization potential of the simulated annealing. Continuous phase should be adopted to increase the light efficiency and decrease wide-angle scattering. The continuous phase DOEs with diameter 100 mm has been obtained by gray-level mask and ion-etching on the K9- glass substrate. The DOEs' interferogram and local profiles are given to detect the precision of manufacturing. The intensity distribution of the focal spot are measured by a general CCD, and a series of attenuators are used to increase the dynamic range of the CCD. The results after data- processing show that the uniform illumination has been obtained.