Multifunctional diffractive optics element for high-energy laser system

Abstract

A diffractive micro-optics element with hybrid functions has been designed to perform Inertial Confinement Fusion (ICF). The functions of a lens, a low efficiency beam sampler, a Color Separation Grating (CSG) and a binary optical element for target uniform illumination has been integrated to the diffractive optical element (DOE). Its phase distribution is continuous on a disk with diameter of 45mm. The focal length of element is 2400mm. Sampling efficiency for 3ω+(0.351um) light at +1 diffraction order is under 0.1% and the space between sampled beam and focal spot is more than 30mm on the target plane. Unwanted harmonic waves of fundamental wave (1ω+) at 1.053 um and second harmonic wave (2ω+) at 0.527 um are diverted out of the high power laser system and the remnant ratio of them at zero order are less than 2%. Meanwhile, the micro-optics element has excellent ability for beam uniform. The side lobe of the 3ω+ focal spot is suppressed very well and the root-mean-square percent error of its top uniformity is less than 1.5%. Although effected by focusing, beam sampling, color separating and beam smoothing, the synthetic efficiency of 3ω+ light is more than 96%. For the functions integrated diffractive micro-optics element, different designing methods have been applied to implement its corresponding aims. The compatibility, fabrication method and influences between the hybrid functions are discussed in detail.