[OPTICAL REVIEW Vol. 15, No. 3 (2008) 156-161]
© 2008 The Optical Society of Japan

Genetic-Algorithm-Based Method to Optimize Spatial Profile Utilizing Characteristics of Electrostatic Actuator Deformable Mirror

Futoshi MATSUI, Shin'ichi GORIKI, Yukio SHIMIZU, Hiromitsu TOMIZAWA1, Sakae KAWATO2, and Takao KOBAYASHI2

Creative and Advanced Research Department, Industrial Technology Center of Fukui Prefecture, Fukui 910-0102, Japan
1Accelerator Division, Japan Synchrotron Radiation Research Institute (SPring-8), Sayo-cho, Hyogo 679-5198, Japan
2Graduate School of Engineering, University of Fukui, Fukui 910-8507, Japan

(Received February 16, 2007; Accepted February 16, 2008)

Arbitrary spatial beam shaping was demonstrated with a membrane electrostatic actuator type deformable mirror (DM). An automatic closed loop system must optimize such beam shapes as flattop. Well-characterized short pulse laser beam is widely required for a photocathode RF gun or for microscopic processing, etc. We propose a new sophisticated optimizing method based on a genetic algorithm (GA) for spatial shaping. A membrane type DM is driven by electrostatic attraction power, and applied electrode voltages vs displacement of membrane surface have a square function relationship. We prepare discrete electrode voltages to linearly change displacement as a utilized gene of the initial population in GA. Using uniform crossover without mutation in this method, we can make an arbitrary spatial beam shape quasi-flattop.

Key words: beam quality control, Ti:sapphire laser, terawatt femtosecond laser, spatial shaping, adaptive optics, three-dimensional pulse shaping, deformable mirror (DM), genetic algorithm (GA), future light sources, photocathode RF gun