Experimental Analyses On Passive Coherent Combining Of All-Fiber Feedback Ring Cavity Based On Diffractive Optical Element

Diffractive optical element is used to realize single-aperture output for passive coherent combining of 8-channel fiber laser. Using this system, we demonstrated the far-field coherent visibility, output spectrum and beam quality after coherent combining. Experimental results show that phase noise will cause the mode frequency to change under multichannel conditions. However, the beam quality and the coherent visibility after coherent combination do not change significantly. The far-field coherence visibility reached 98.6%, the beam quality M-2=1.21, and the diffraction limit magnification factor ss reached 1.98. This shows that in the presence of low phase noise, even if the number of channels is increased, a coherent combined output with high beam quality can be obtained.