Design of kinoform phase plate arrays for spatial beam smoothing

It has been widely accepted that spatial beam smoothing is essential in coupling laser energy to inertial confinement fusion targets. In this paper, kinoform phase plate arrays have been proposed to produce spatially homogenized far fields for a broad range of phase and irradiance non-uniformities in the incident beam. A global-local united search algorithm has been presented to design a phase plate element to concentrate more than 95% energy of laser beams on a flat-top super-Gaussian (SG) envelope. A spatial-fining technique has been proposed to control the intermediate-spatial-frequency overlapping intensity modulation generated by various phase plate elements. For a flat incident aperture size of 40 cm, a laser wavelength of 351 nm, and a lens focal length of 1000 mm, 10 x 10 phase plate arrays have been designed to produce sixteenth-order SG profiles with the intensity modulation interval less than 5 mu m. More than 96% of the incident energy is homogeneously constrained in the desired region.