Yb- and Er-doped fiber laser Q-switched with an optically uniform, broadband WS₂ saturable absorber

We demonstrate a ytterbium (Yb) and an erbium (Er)-doped fiber laser Q-switched by a solution processed, optically uniform, few-layer tungsten disulfide saturable absorber (WS₂-SA). Nonlinear optical absorption of the WS₂-SA in the sub-bandgap region, attributed to the edge-induced states, is characterized by 3.1% and 4.9% modulation depths with 1.38 and 3.83 MW/cm² saturation intensities at 1030 and 1558 nm, respectively. By integrating the optically uniform WS₂-SA in the Yb- and Er-doped laser cavities, we obtain self-starting Q-switched pulses with microsecond duration and kilohertz repetition rates at 1030 and 1558 nm. Our work demonstrates broadband sub-bandgap saturable absorption of a single, solution processed WS₂-SA, providing new potential efficacy for WS₂ in ultrafast photonic applications.