Coherent beam combining of MOPA with multi-dithering technique

Coherent beam combining of two and three watt-level fiber amplifiers is demonstrated with multi-dithering technique used for phase control. In the experiment, the master laser is split into two or three channels and the power of each channel is amplified by a fiber amplifier. When the control loop is open, the far-field pattern is dynamic and blurred, and the fringe contrasts for combining are 0.19 for two beams and 0.12 for three beams. When the control loop is closed, the far-field pattern is stable and clear, the fringe contrasts for two- and three-beam combinings are improved to 0.93 and 0.81 respectively and the corresponding coherent combining efficiencies are 80% and 77%. In addition, the experimental results of two- and three-beam combining are compared and the effect of each control on coherent beam combining is given.