I demonstrate the closed-loop control of a programmable liquid-crystal spatial light modulator using real-time SHG FROG. Control theory states that proportional only controllers are almost never suitable for very tight control because any calibration errors can result in offsets between the input (desired result) and output. In this work, the pulse output from the real-time FROG software is sent to proportional-integral controller for maintaining the spectral phase of a pulse. The additional integral control term removes the constant offset that plagues proportional only controllers. The response time of pulse shaping system is a few seconds, limited only by the speed of the pulse shaper.

Date Published: 28 February 2006
PDF: 6 pages
Proc. SPIE 6108, Commercial and Biomedical Applications of Ultrafast Lasers VI, 61080D (28 February 2006); doi: 10.1117/12.660195

Published in SPIE Proceedings Vol. 6108:
Commercial and Biomedical Applications of Ultrafast Lasers VI
Joseph Neev; Stefan Nolte; Alexander Heisterkamp; Christopher B. Schaffer, Editor(s)