A microfiber knot incorporating a tungsten disulfide saturable absorber based multi-wavelength mode-locked erbium-doped fiber laser

A novel multi-wavelength mode-locked Erbium-doped fiber laser with tungsten disulfide (WS2) combined with a microfiber knot is described. This hybrid fiber structure facilitates strong light matter interaction between the saturated absorption of the WS2 material and high optical non-linearity of the microfiber knot. It is demonstrated experimentally that the novel fiber laser works stably in the absence of an external comb filter, with the generation of stable multi-wavelength picosecond pulses. In the multi-wavelength lasing regime, up to 7-wavelength stable mode-locked pulses are obtained using a polarization controller with the pump power at ~250 mW. The pulse period and the pulse width are 188.7 ns and 16.3 ps respectively. In addition, the number of multi-wavelength lasing channels can be changed by simply adjusting the microfiber knot size. Experimental results show the laser to have a stable output over 12 hours recording period. The results of this investigation demonstrate that the optical microfiber knot with a WS2 overlay based fiber laser device can operate as a highly nonlinear optical component and a saturable absorber. The proposed multi-wavelength lasing device can therefore be widely used for non-linear and ultrafast photonics and has a number of advantages compared to similar devices using more conventional technologies, including low cost and good stability