Mode-locked all-fiber lasers at both anomalous and normal dispersion regimes based on spin-coated MoS₂ nano-sheets on a side-polished fiber

We demonstrate an all-fiberized mode-locked laser by employing Molybdenum Disulfide (MoS₂) spin-coated onto a side-polished fiber (SPF) as an in-line saturable absorber. Single crystal MoS₂ has been exfoliated via the Li intercalation method and then dispersed with large population of few-layer MoS₂ nano-sheets in ethanol. Subsequently, a saturable absorber has been prepared using a relatively simple method: spin-coating the uniform MoS₂ solution on the fabricated SPF without using any polymer or toxic procedure. Power-dependent transmission property of the prepared MoS₂ nano-sheets on the SPF was experimentally analyzed, providing the feasibility to apply it as an efficient in-line saturable absorption behavior. By deploying the MoS₂ SPF into a fiber laser cavity with finely tuned laser pump power and cavity dispersion, mode-locked pulses were obtained at anomalous and normal dispersion of the laser cavity. The self-started soliton pulses at the anomalous dispersion regime were generated with a spectral bandwidth of 9.96 nm at 1584 nm and a pulse duration of 521 fs. Moreover, by managing the dispersion to the normal regime, stable pulses at net-normal intra-cavity dispersion with 11.9 ps pulse duration were obtained with a spectral bandwidth of 18.2 nm at 1570 nm. The results prove the effectiveness of developing MoS₂ saturable absorbers and applications for pulsed laser operation.