Coherent Beam Combining of a Fiber Lasers Array Based on Cascaded Phase Control

A novel approach for active coherent beam combining of a large number of fiber lasers based on cascaded phase control is demonstrated. The principle of this approach is briefly introduced, and its feasibility is verified by coherent beam combining of 16 fiber lasers. In the experiment, eight fiber lasers in each sub-array are coherently combined by employing stochastic parallel gradient descent algorithm with a residual phase error of λ/28, and then, the combined beams from the two sub-arrays are phase locked by using a single-frequency dithering technique with a residual phase error of λ/24. It is scalable to phase lock of hundreds of fiber lasers, because high control bandwidth can be obtained by using cascaded phase control.