Impact of Phase Perturbation on Passive Phase-Locking Coherent Beam Combination

The impact of phase perturbation on passive phase- locking coherent beam combination is studied. A ring cavity passive phase-locking coherent beam combination system of an array of two fiber lasers is built. The phase perturbation is experimentally simulated with a phase modulator. Experimental results show that the contrast ratio of central fringe in the far- field beam patterns decreases with an increase of the perturbation frequency or amplitude. Theoretical analysis is given.