Multi-wavelength bright-dark pulse pair fiber laser based on rhenium disulfide

As a new member of transition metal dichalcogenides (TMDs), rhenium disulfide (ReS₂), with a nearly unchanged direct bandgap from bulk to monolayer form, is attractive in physics and material fields. By using the optically driving deposition method, the ReS₂ saturable absorber (SA) has been fabricated with a modulation depth and saturation fluence of 6.9% and 27.5 μJ/cm², respectively. Based on the ReS₂-SA, a multi-wavelength bright-dark pulse pair from a mode-locked fiber laser has been observed experimentally for the first time, to the best of our knowledge. The saturable absorbing ability of the ReS₂ is attributed to the formation of the bright pulses and the dark pulses. The cross-phase modulation (XPM) caused by different wavebands of bright pulse and dark pulse support the coexisting of the bright-dark pulse pair.