High-power All-fiber Figure-eight Mode-locked Fiber Laser

The generation of high-energy high-peak ultrafast pulses has been a research hotspot in the field of optics.Dissipative soliton resonance(DSR)as a square wave pulse with theoretically infinitely increasing energy and constant peak power,is expected to break through the energy limitation compared with other traditional pulses.At present,there is still a lot of room for improvement in properties of DSR,and research on its evolution dynamics and practical application is still at the beginning.Therefore,exploring the pulse evolution mechanism,obtaining high-performance pulses and verifying the feasibility of pulse application is the main goal of this research.The main research contents of this thesis are as follows:Based on the simulation model of figure-eight laser,the pulse state transition is analyzed by drawing pulse characteristics distribution under two-dimensional pump power spaces.We firstly find that the pulse peak power and width vary dependently and non-monotonously under asymmetric coupling ratio.Under different pump power combinations,the transmittance curve of the equivalent saturable absorber is shifted and distorted under the influence of pump power coupling and gain saturation.The utilization of dual-pump could effectively enlarge the saturable power as well as the transmittivity,which provide a novel road to increase the DSR peak power.The dual-amplifier figure-eight mode-locked fiber laser built according to the simulation could generate DSR pulses with record peak powers ranging from 300 W up to 1500 W.After removing the filter in unidirectional loop and changing the fiber in the other loop,switchable generation of versatile patterns of DSR and noise-like pulses(NLPs)were first achieved in one cavity.Pumping by rectangular DSR pulses,selective excitations of Raman Stokes lines of up-to 3rd order with extinction ratio of 8 d B were demonstrated experimentally.More exact flat-topped pulses facilitate more complete conversion since standard square pulse possesses a lower energy ratio of the rising and falling edges.After separating the propagated pulse by bandpass filters,shorter spectral components were confirmed to be located in the pulse trailing edge after propagating,consistent with the theory.An all-fiber and spectral distribution invariable supercontinuum(SC)was generated by directly pumping 1kw peak power DSR into PCF.The SC remained nearly invariable spanning from 450 to 2250 nm while enlarged the total intensity with an increasing output power from 0.65 to 1.74 W.