Abstract

In high power laser system, such as laser forming, the requirement for the intensity distribution of the focused laser profile must be top head, steep edge, low side lobe and concentrated high power performance in the main lobe. Such uniform illumination can be realized by the Diffractive Optical Element (DOE), because the DOE has many advantages, such as high light efficiency of pure phase modulation, strong flexibility of phase distribution design and so on. In some application field, uniform illumination is needed on the plane non-perpendicular to the optical axis and the DOE designed by conventional method which only involves the focal plane is difficult to realize such uniform illumination on the planes which are at angles of 30 degree(s), 45 degree(s), 55 degree(s) with the optical axis. To obtain good illumination uniformity on the inclined plane, based on the method of designing a DOE with long focal depth, an indirect design principle is proposed to realize such uniform illumination, by designing the phase distribution of the DOE to make uniform illumination on three planes at right angles with the optical axis, then the uniform illuminations on the incline planes are assured. A hybrid algorithm based on hill-climbing and simulated annealing is utilized for phase design which exploits the ability of strong convergence of the hill-climbing and the global optimization potential of the simulated annealing sufficiently. Simulated results show the non-uniformity on the incline planes at angles of 30 degree(s), 45 degree(s), 55 degree(s) with the optical axis are 5.91%, 4.00%, 3.38%, respectively.

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