Passive mode-locking and Q-switching of ytterbium-doped fiber lasers using Cr₂S₃ saturable absorbers

In recent years, 2D Cr₂S₃ has earned lots of attentions in the fields of photocatalysis and photodetector due to its outstanding environmental stability and high responsivity. However, up to now, the optical properties of 2D Cr₂S₃, especially the NLO properties of Cr₂S₃ have been rarely studied. In this work, the NLO properties of Cr₂S₃-nanoparticles in 1 μm have been investigated by using open-aperture (OA) Z-scan method. The nonlinear absorption coefficient (β), modulation depth and saturable intensity are measured to be -2.6 \(\times {10}^{4}\) cm/GW, 11.5%, and 0.115 MW/cm², respectively. Furthermore, by depositing Cr₂S₃ nanoparticles on a side-polished fiber and inserting into a ytterbium-doped fiber laser (YDFL) cavity, stable mode-locking laser and Q-switching laser with a pulse width of 10.2 ns and 2.95 µs are achieved, respectively. These results demonstrate that Cr₂S₃ is a promising saturable absorber (SA) for the fiber laser applications.