Square pulse generation from all-normal-dispersion graphene oxide mode-locked Yb-doped fiber laser

Square pulse generation from mode-locked fiber laser has been theoretically and experimentally studied for a few years. The phenomenon was explained theoretically as so called “dissipative soliton resonance (DSR)” [1]. Most experimental work concentrated on 1.5μm wavelength, with a few on 1μm, and both could be operated in positive or negative dispersion regimes. Most of them adopted nonlinear polarization evolution as the mechanism for mode-locking, and the nonlinear loop mirror was reported as well.