Research Of 2D Material-Based Passively Mode-Locked Fiber Laser

Passively mode-locked fiber laser(PMLFL) is a kind of very important laser. It has widespread applications in nonlinear optics, high-speed communication, optical fiber, biomedicine engineering, laser micromachining and lidar because they can produce ultrashort pulses with high peak power and broad optical spectrum. Recently, novel two-dimensional(2D) materials such as graphene, transition metal sulfide(including layered molybdenum disulfide(Mo S2), tungsten disulfide(WS2) and so on) have vastly drawn many scientists’ attention due to their great electronic and optical properties. The study of PMLFLs based on 2D materials becomes the research focus nowadays. So it is of great scientific and practical importance to research them. The main research contents of this thesis are as follows:First, the few-layer Mo S2 was grown by the chemical vapor deposition(CVD) method, and its material property and optical absorption was characterized. Then a passively mode-locked erbium-doped fiber laser(EDFL) based on few-layer Mo S2 was built and utilized to generate stable mode-locked solition pulses. The produced soliton pulses have central wavelength, spectral width and pulse duration of 1571.3 nm, 2.8 nm and 0.91 ps respectively. In addition, the relationship between the pulse duration and the cavity net dispersion is discussed and the results of numerical simulation are compared to the experimental observations to verify the relationship.Besides, the graphene, layered Mo S2 and WS2 were grown by the chemical vapor deposition(CVD) method, and were transferred to fabricate graphene/Mo S2 heterojunction and graphene/WS2 heterojunction by special technology. Then, the two heterojunctions’ material properties and optical absorptions were characterized. After that, a passively mode-locked erbium-doped fiber laser(EDFL) based on the two heterojunctions were built and utilized to generate stable mode-locked solition pulses respectively. The graphene/Mo S2 heterojunction based passively mode-locked EDFL produced soliton pulses with central wavelength, spectral width and pulse duration of 1571.8 nm, 3.5 nm and 0.84 ps respectively. The graphene/WS2 heterojunction based passively mode-locked EDFL produced soliton pulses with central wavelength, spectral width and pulse duration of 1561.5 nm, 3.4 nm and 0.78 ps respectively.Lastly, the physical model of the wavelength tunability caused by birefringence effect in a graphene-based mode-locked fiber laser is built. The wavelength tunability of the fiber laser was numerical simulated, and the results were compared with the reported experimental results. The results show that by utilizing fiber birefringence, the central wavelength of mode-locked pulses could be continuously tuned over the range from 1554 to 1566 nm in anomalous dispersion regime, while the range is from 1556 to 1564 nm in normal dispersion regime. The numerical results are in agreement with the reported experimental observations.