To design a fully continuous wave-front distribution suitable for focused beam shaping by a deformable mirror, we modify the phase-retrieval algorithm by employing a uniformly distributed phase as a starting phase screen and spatial filtering for the near-field phase retrieved during the iteration process. A special phase unwrapping algorithm is not required to obtain a continuous phase distribution from the retrieved phase since the boundary of the 2π-phase-jumped region in the designed phase distribution is perfectly closed. From the computational result producing a uniform square beam transformation from a circular defocused beam, this algorithm has provided a fully continuous wave-front distribution with a lower spatial frequency for a deformable mirror. The transformed square beam has a normalized intensity nonuniformity of σrms = 0.14 with respect to a desired flat-topped square beam pattern. This beam-shaping method also provides a high energy-concentration rate of more than 98%.
© 1998 Optical Society of America
Original Manuscript: June 12, 1997
Revised Manuscript: October 29, 1997
Published: March 10, 1998
Geun-Young Yoon, Sinichi Matsuoka, Takahisa Jitsuno, Masahiro Nakatsuka, and Yoshiaki Kato, "Wave-front design algorithm for shaping a quasi-far-field pattern," Appl. Opt. 37, 1386-1392 (1998)