Diffractive phase screen for superresolution focal spot

A new design of diffractive superresolution elements with surface-relief phase screen has been presented to improve the quality of the superresolved diffractive patterns. The diffractive phase screens have been designed by our proposed global optimization method, called Global/Local United Search Algorithm. The new algorithm combines the global exploration properties of Genetic/Annealing algorithms and the accurate exploitation power of the 'hill-climbing' method, resulting in the characteristics of fast convergence, global search capability, and high performance diffractive patterns. The designed diffractive phase screens can improve the performance of the superresolved diffractive patterns from the view of Strehl ratio, reduction of the focal spot, and control of the sidelobe intensity. The results show that the diffractive phase screen can produce much small spot size and great lower sidelobe intensity while keeping an acceptable Strehl ratio, which has important applications in high density data storage.