Impact of phase perturbation on passive phase locking of fiber laser array

The impact of phase perturbation on passive phase locking of fiber laser array is studied theoretically and experimentally. The phase perturbation is experimentally simulated by using a phase modulator. A ring cavity passive phase locking coherent beam combining system of an array of two fiber lasers is built. Experimental results show that the contrast ratio of central fringe in the far-field beam patterns decreases with increasing the perturbation frequency or amplitude. For the modulation depth of π/2, stable interference fringes with high contrast ratio can be still obtained even at modulation frequency of about 50 kHz in our experiment.