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