Ku-Hui HSU and Hoang Yan LIN^*

Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan, R.O.C.

(Received December 5, 2012; Accepted May 8, 2013)

The trade-off between diffraction efficiency and uniformity is studied when a binary phase-only diffractive optical element (DOE) is designed for transforming a Gaussian beam to an expanded squared uniform intensity distribution. The simulated annealing (SA) algorithm and Fresnel diffraction theory are applied in our design. Two types of cost functions are utilized in the SA algorithm, and the cases of different incident Gaussian diameters and bright-area sizes of the target patterns are studied. The mechanisms of reducing nonuniformity by the two cost functions are essentially different, and the mechanism combining nonuniformity and the intensity difference between the reconstructed and target patterns has better results. Satisfactory performance can be obtained under the trade-off between them.

Key words: diffractive optical element, laser beam shaping, binary optical element, Fresnel diffraction, simulated annealing algorithm

^*E-mail address: hylin@cc.ee.ntu.edu.tw