Coherent beam combination of two fiber amplifiers with multi-dithering technique

Coherent beam combination of two W-level fiber amplifiers with multi-dithering technique is demonstrated.In the experiment,the master laser is split into two channels.Multi-dithering technique is used for phase control.One channel is modulated with a 100 kHz sine wave produced by signal generator,and DSP lock-in amplifier is used for electric signal processing in the feedback loop.When the phase control loop is off,the far field interference pattern is blurred and dynamic with 20% fringe contrast.When the feedback loop is closed,the far field interference pattern is clear and stable with 72% fringe contrast,and 75% coherent combination efficiency is achieved.