Passive Coherent Polarization Beam Combination of a Four-Fiber Amplifier Array

We present what we believe to be a new architecture for coherent beam combination of a fiber amplifier array. Four polarization-maintained fiber amplifiers are passively coherent polarization beam combined by using an optical feedback in a ring cavity. Experimental results verify that the architecture is robust and effective. The combining efficiency of the whole system can be as high as 91%, and the phase noise can be suppressed effectively. We believe that the configuration presented in this paper is a promising approach for high-power laser combination without degrading the beam quality of the coherently combined beam.