Coherent beam combination of three ytterbium fiber amplifiers

Coherent beam combination of fiber laser array is an important technology in realizing high power fiber laser system. In this paper, master oscillator-power amplifier scheme is used to realize phase control of three ytterbium fiber amplifiers. In the experiments, the output power of each ytterbium fiber amplifier is not less than 1 W and the total output power of the three amplifiers is not less than 3 W. Phases are controlled by LiNbO3 phase modulator. The heterodyne detection control system works at 40 MHz and the control precision is l/20. The fibers are polarizedly maintained. The experimental results of both two and three fiber amplifiers are given. When the control loop is off, the far field interference pattern is dynamic and blurred. While the control loop is on, the far field