Passively Mode-Locked Fiber Laser with WS₂/SiO₂Saturable Absorber Fabricated by Sol-Gel Technique

High-performance ultrafast fiber lasers require saturable absorbers (SAs) of high optical damage threshold and high operation stability. Here, the optical properties and application of the WS2/SiO2 SA prepared by the sol-gel method are reported. SiO2 prepared by sol-gel technique has similar properties to fiber in ultrafast fiber lasers, such as mechanical strength, refractive index, optical transmission, and absorption. For the SA device by the sol-gel method combined with WS2 material, not only will the additional scattering loss not be introduced, but also, the damage threshold of the SA device can be effectively increased. Furthermore, SA material is wrapped by SiO2, which insulates the influence of the external environment. Based on the first preparation of the WS2/SiO2 glass SA, stable soliton pulses are obtained in ytterbium-doped fiber lasers (YDFLs) with a pulse width of 58 ps, an average output power of 56.8 mW, and a repetition rate of 19.03 MHz. In addition, a stable mode-locked operation with a pulse width of 325 fs and an output power of 39.6 mW is also achieved in an erbium-doped fiber laser (EDFL). These results demonstrate that the WS2/SiO2 glass prepared by the sol-gel method can significantly increase laser output power and shorten pulse width in the fiber laser, which provides a new opportunity for the traditional preparation method of the SA device.