Experimental exploration of mode-locking evolution mechanism in dual-ring fiber laser

Abstract

We explored experimentally the mode-locking (ML) evolution mechanism of a dual-ring fiber laser. Increase of the total pump power up to 860 mW allowed the observation of the state changes from single-ring ML, dual-ring ML, to dual-ring self-starting ML. Moreover, a group of wave plates and a fixed polarization beam splitter were applied in each subring as precise attenuators. Rotation of each wave plate for an entire turn allowed the investigation of the ML evolution of the two subrings based on the intracavity power variation in each subring. The variation periodicity of the output power was analyzed for each subring and was found to be consistent with the theoretical results. Furthermore, the ML detachment threshold in each subring was estimated to explain the ML evolution. Our study provides a deeper understanding of the ML evolution in dual-ring fiber lasers and can aid their future optimal design for dual comb applications.