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Proceedings Paper

Diffractive optical element array to realize uniform focal spot with any geometrical shape transform
Author(s): Qiaofeng Tan; Yingbai Yan; Guofan Jin; Minxian Wu
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Paper Abstract

Uniform focal spot which has top flat, steep edge, low sidelobes and other features is needed in many fields, such as Inertial Confinement Fusion and laser manufacturing. For different application, different input conditions and output demands are requested, for example, the laser put in or/and uniform focal spot put out has any kinds of geometrical shape, including circular, square, elliptical and so on. Such uniform focal spots with a certain geometrical shape transform can be realized by using Diffractive Optical Elements (DOEs) array, which has many advantages, such as high light efficiency of the pure phase modulation, strong flexibility of the phase design and geometrical shape transform and so forth. 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. Geometrical shape transform is based on the principle of any geometrical shape can be approximated to by some series of square cells with different positions, different or same sizes. The phase design is simplified by adopting square cells, because two- dimensional problem is converted to one-dimensional problem. Two typical cases are concerned, i.e. circular laser put in with square uniform focal spot put out and square laser put in with circular uniform focal spot put out. Simulated results show this method and the hybrid algorithm are very valid. 6

Paper Details

Date Published: 7 May 1999
PDF: 4 pages
Proc. SPIE 3740, Optical Engineering for Sensing and Nanotechnology (ICOSN '99), (7 May 1999); doi: 10.1117/12.347807
Show Author Affiliations
Qiaofeng Tan, Tsinghua Univ. (China)
Yingbai Yan, Tsinghua Univ. (China)
Guofan Jin, Tsinghua Univ. (China)
Minxian Wu, Tsinghua Univ. (China)

Published in SPIE Proceedings Vol. 3740:
Optical Engineering for Sensing and Nanotechnology (ICOSN '99)
Ichirou Yamaguchi, Editor(s)

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