Dual-Wavelength Soliton Mode-Locked Fiber Laser With a WS2-Based Fiber Taper

Recently, few-layer WS
₂
, as a novel two-dimensional (2D) material, has been discovered to possess both the saturable absorption effect and the huge nonlinear refractive index. In experiment, by taking advantage of the unique optical properties of 2D WS
₂
, we fabricated a highly nonlinear photonic device using the pulsed laser beam to deposit the WS
₂
film onto a fiber taper. With the WS
₂
-based fiber taper, we have demonstrated the single-and dual-wavelength soliton pulses in the erbium-doped fiber laser (EDFL) by properly adjusting the pump strength and the polarization state. According to the soliton theory, the pulse width is ~220 fs for the single-wavelength soliton, and ~585 and ~605 fs for the dual-wavelength soliton, respectively. The dual-wavelength soliton fiber laser exhibits the maximum output power of 10.1 mW and the pulse energy of ~1.14 nJ, when the pump power is increased to ~420 mW. Our findings suggest that WS
₂
-based fiber taper could operate as both an excellent saturable absorber for obtaining a femtosecond pulse and a promising highly nonlinear photonic material for the multi-wavelength generation.