Polarization Domains and Polarization Locked Vector Solitons in a Fiber Laser

We have experimentally observed, for the first time, the coexistence of polarization domains (PDs) and polarization locked vector solitons (PLVSs) in an Er-doped fiber laser with microfiber-based graphene as a saturable absorber (SA). Taking advantage of the high nonlinearity and the saturable absorption of the microfiber-based graphene SA, we observed both PDs and their splitting into regularly or irregularly distributed multiple PDs under relatively high pump power; at lower pump power with careful adjustment of the intra-cavity polarization controllers, we observed PLVSs either as disordered soliton bunch or with harmonic mode locking. The conditions under which these patterns formed have also been experimentally investigated in detail.