The sine–cosine single-frequency dithering technique for active phase locking of fiber amplifiers is presented for the first time to our knowledge. It has twice the phase control speed as the single-frequency dithering technique. Detailed theoretical development has been presented and the relevant experiment has been done. In the experiment, nine 10 W level fiber amplifiers are tiled into 3×3 array and the total output power is about 100 W. The sine–cosine single-frequency dithering algorithm is run on a signal processor based on a field-programmable gate array for phase control on the fiber amplifiers. When the phase control system is in a closed loop, the fringe contrast of far-field intensity pattern is improved by more than 90% from 21% in an open loop, and the residual phase error is less than λ/20.
© 2011 Optical Society of America
Lasers and Laser Optics
Original Manuscript: February 3, 2011
Revised Manuscript: May 11, 2011
Manuscript Accepted: May 11, 2011
Published: July 1, 2011
Yanxing Ma, Pu Zhou, Xiaolin Wang, Haotong Ma, Xiaojun Xu, Lei Si, Zejin Liu, and Yijun Zhao, "Active phase locking of fiber amplifiers using sine–cosine single-frequency dithering technique," Appl. Opt. 50, 3330-3336 (2011)