Saturable Absorbers Based On Two-dimentional Materials For Pulsed Fiber Lasers

Ultrashort pulsed fiber lasers have widespread applications in the fields of optical communication,material processing,biomedical research and spectroscopy.One majority type of ultrashort pulsed fiber lasers employs a nonlinear optical element,called saturable absorbers(SAs),to turn the continuous wave into a train of ultrashort optical pulses,due to their compactness,simplicity and cost-efficiency.Here,we investigated graphene,transition metal carbides and their heterostructures as saturable absorbers applied in fiber lasers for ultrafast pulse generation,which can be briefly introduced as following:1.Large-area,high-quality graphene films were grown on copper substrate using the chemical vapor deposition(CVD)method.Then graphene-based SAs were prepared by the typical wet transfer method onto the facet of an optical fiber.By inserting graphene SAs into 1550 nm Q-switched fiber laser,stable Q-switched pulses were generated with high pulse energy.2.We investigated the nonlinear optical properties of high quality 2D ?-Mo2 C crystals grown by CVD method.Z-scan experiments were implemented and tunable modulation depth was observed in 2D ?-Mo2 C.In combination with its ultrafast carrier recovery time and broadband light absorption,2D ?-Mo2 C shows excellent saturable absorption properties as a potential wideband SA.We then demonstrated the usage of2 D ?-Mo2 C SAs in fiber lasers to generate ultrashort mode-locking pulses at 1060 nm and 1550 nm,respectively.3.We used the CVD-grown graphene/2D ?-Mo2 C vertical heterostructures as SAs applied in ultrafast fiber lasers.Graphene/2D ?-Mo2 C vertical heterostructures show excellent saturable absorption properties in terms of larger nonlinear absorptioncoefficient and lower saturable absorption intensity,in comparison with the single graphene or 2D ?-Mo2 C.It was also found that this kind of SAs can generated femtosecond pulses with long-term stability at 1550 nm,which showed better overall output performance than graphene-based and ?-Mo2C-based pulsed fiber lasers.