Coherent beam combination of fiber laser array with multi-dithering

Coherent beam combining of four fiber laser beams with multi-dithering based on field programmable gate array(FPGA) control module was demonstrated. When the phase control system is in close loop, the phase errors between the beams induced by atmospheric turbulence and mechanical vibrations are compensated and the contrast of the far-field coherent combined beam profile is improved to 0.93 from 0.21 in the open loop, and the power in the given area is 3.3 times higher. Even if the fibers are dithered, the contrast of far-field beam profile is still held at 0.72.