Research On Figure-of-nine Fiber Laser Based On Dispersion Compensation

Ultra-fast pulsed fiber laser is widely used in various fields,such as ultrafast optical imageing,optical microscope,etc.,because of their narrow pulse width,wide spectrum and high peak power,and thus has gained extensive from scholars at home and abroad.Therefore,how to obtain ultra-fast pulsed fiber laser with better porformance has become one of the research hotsports around the world.Recently,mode-locking technologies and Q-switching technology are the most common and used technology to obtain fiber lasers with ultrashort pulse.The Q-switching technology is traped in the experimental material,but the other one does not.Active mold locking technology,self-locking technology and passive mold locking technology are the main technologies of mode-locking technology,only the last one is the most stable to the environment.In passive mode-locking technology,the figure-8 cavity laser has advantage of high environment stability,low cost and narror output pulse,so it has good application prospect and commercial value.The recently improved fiber laser based on nonlinear amplification ring cavity(figure-9 cavity laser)is a modification of figure-8 cavity laser,which optimizes the cavity structure on the original basis,and achieves higher repetition frequency.At present,the laser based on figure-9 cavity structure has poor environmental stability,and the output pulse contains Kelly sideband.On this basis,a fully polarized "9" cavity laser with stable environment,self-starting and Kelly-free edges based on dispersion compensation is obtained.The main work and achievements of this paper are as follows:1.Introduce the laser structure based on nonlinear ampily loop mirror,and deduce the mode-locking principle of figure-9 cavity structure.2.Based on the figure-9 cavity laser,a figure-9 cavity with full polarization preservation based on dispersion compensation is constructed.Finnally,the experiment obtained the femtosecond lasers with full polarization preservation,all-fiber,self-starting,Kelly-free sideband and broadened pulse dispersion mode-locked.The laser has a repetition frequency of 46.6MHz,a spectral width of 25.7nm,and a compressed time-domain width of 167fs.3.The dispersion compensation mechanism is innovatively introduced into the all-polarization figure-9 cavity laser,eliminating the Kelly sideband in the traditional figure-9 cavity laser and obtain a wider and smoother pulse spectrum.At this time,the output pulse spectral bandwidth of the laser is 39nm,the compressed time-domain width is 95 fs,and the repetition frequency is 41MHz.The pulse width is improved by about 60%compared with that before the introduction of dispersion compensation in this paper,and the obvious improvement is obtained.