Noise-like Mode-locked Fiber Laser Based On Transition-metal Dichalcogenides

Ultrashort-pulse fiber lasers have very important application value in optical fiber sensing,material micromachining and biomedical detection because of their high peak power,single pulse energy and wide spectrum.The passive mode-locking mechanism can be divided into nonlinear polarization rotation mode locking,nonlinear optical ring mode mode locking,and saturable absorber mode locking.Among them,the saturable absorber of the material is widely used due to its low cost,simple structure,and stability that is not easily affected by external influences.The two-dimensional nano-material saturable absorber has the advantages of wide working band,fast recovery time,simple preparation process,low cost,easy integration,and all-fiber,and has become a current research hotspot and an important frontier field in the world.Studying the parameters of saturable absorbers and the characteristics of saturable absorbers for two-dimensional nanomaterials has important guiding significance and practical value for the preparation of saturable absorbers and the control of pulsed performance of fiber lasers.In this paper,theoretical and experimental investigations have been conducted on the application of a transition metal sulfide saturable absorber in a two-dimensional material to pulse generation of a 1 ?m ytterbium-doped fiber laser.The research content mainly includes:1.The research background and the application of transition metal sulfides in fiber lasers were investigated.The saturable absorption characteristics of transition metal sulfides,their preparation methods and their application to fiber lasers were introduced in detail.2.The basic principles of passive mode locking and passively mode-locked fiber lasers based on different dispersion fields are introduced in detail.Aiming at the noiselike pulse in the field of total positive dispersion,a detailed analysis was carried out and a corresponding theoretical simulation was performed.3.Noise-like mode-locked pulses are obtained in tungsten-doped ytterbium-doped fiber lasers.Stable fundamental frequency mode-locking has a pulse width of 20 ns and a repetition rate of 7 MHz.The autocorrelation curve spike of the output pulse shows an average pulse width of 550 fs.The second order harmonic noise-like mode locking has a 1.3 nm spectral bandwidth and a pulse width of 10 ns.With a pump power of 400 mW,the maximum output power is 22.2 mW.4.In the same fiber laser,dissipative soliton mode-locked pulses were obtained with a pulse width of 560 ps.A typical all-optical dispersion spectrum has a width of 2 nm and a repetition rate of 7 MHz.