Analysis of the effects of aberrations on coherent polarization beam combining of fiber laser beams

In this paper, the influence of aberrations on coherent polarization beam combining (CPBC) of fiber laser beams is analyzed in detail for the first time to our knowledge. The expression of the coherently polarization combined output power is obtained, which contains the geometry and nongeometry factors of the CPBC system. The geometry and nongeometry aberrations are numerically studied to investigate their effects on the combining efficiency. It is found that to ensure the combining efficiency of a CPBC unit (we studied) to be more than 90%, the overlap error (the beams in the polarization beam combiner cannot be superposed entirely) should be controlled to be less than 0.45, the tilt error should be less than 2π/15 rad, and the RMS value of the phase error should be limited to be within λ/10. The generalized methodology that we present offers a good reference for investigating the CPBC system in an extensive way.