Mode-locking pulse generation with MoS2-PVA saturable absorber in both anomalous and ultra-long normal dispersion regimes.

Abstract

We experimentally demonstrate a stable and simple mode locked erbium doped fiber laser (EDFL) utilizing passive few-layer molybdenum disulfide (MoS2) as a saturable absorber. The MoS2 is obtained by liquid phase exfoliation before it is embedded in a polymer composite film and then inserted in the laser cavity. A stable soliton pulse train started at a low threshold pump power of 20mW in the anomalous dispersion regime after fine-tuning the rotation of the polarization controller. The central wavelength, 3dB bandwidth, pulse width, and repetition rate of the soliton pulses are 1574.6nm, 9.5nm, 790fs, and 29.5MHz, respectively. By inserting a 850m long dispersion shifted fiber (DSF) in the cavity, a dissipative soliton with square pulse train is obtained in the normal dispersion regime where the operating wavelength is centered at 1567.44nm with a 3dB bandwidth of 19.68nm. The dissipative soliton pulse has a pulse width of 90ns at a low repetition rate of 231.5kHz due to the long DSF used. These results are a contribution to the pool of knowledge in nonlinear optical properties of two-dimensional nanomaterials especially for ultrafast photonic applications.