MoS2/graphene heterostructure incorporated passively mode-locked fiber laser: from anomalous to normal average dispersion

Two-dimensional (2D) nanomaterials for ultrafast photonic applications have attracted significant attention in recent years. 2D nanocomposites are of great interest because of their capability to combine the merits of each nanomaterial. In this work, we have demonstrated erbium-doped mode-locked fiber lasers that incorporate MoS2/graphene heterostructure based saturable absorbers (SAs) from anomalous to normal average dispersion for the first time. The modulation depth, the saturation intensity, and the non-saturable absorption of the MoS2/graphene heterostructure are measured to be 12.4%, 12.7 MW/cm2 and 28%, respectively. By incorporating this particular MoS2/graphene heterostructure based SA, the mode-locked fiber lasers can produce stable pulse trains at anomalous, near-zero, and normal average dispersion. At an anomalous average dispersion of -0.181 ps2, the Kelly sidebands are found to be superimposed on the optical spectrum, and a stable soliton pulse train has been measured with a signal-to-noise ratio of ∼73 dB in the radio frequency spectrum. At a near-zero average dispersion of -0.082 ps2, a Gaussian-like optical spectrum has been observed where the narrowest pulse width is ∼837 fs. At normal average dispersion of + 0.041 ps2, the steep-edge optical spectrum has been produced, indicating that dissipative solitons have been generated. The obtained results prove that a MoS2/graphene heterostructure is an ideal SA in mode-locked fiber lasers for ultrashort pulse generation from anomalous to normal average dispersion