Research On The Novel Passively Mode-locked Fiber Laser

The discovery of pulse operation fiber laser enables the energy to focus on a short time,which improves the peak power effectively.Passively mode-locked fiber laser is used as an excellent method to achieve ultra-short optical pulse due to the variety applications such as communication system,industrial processes,detection,medical,military and science research.In this paper,on condition that the development tendency is considered;we explain the principle of passively mode-locked fiber laser and show several important ways to obtain passive mode-locking.Besides that,we numerical simulate the figure eight fiber laser(F8L)and experimentally demonstrate it.The mainly works include the research of the methods of achieving mode-locked optical pulse and multi-types pulse fiber laser.The main achievements and conclusions are listed as follows:(1)We have summarized the development of passively mode-locked fiber laser and research significance of our work,furthermore,the research status at home and abroad have been detailed as well as the applications of the passively mode-locked fiber laser.(2)We have introduced the principle of passively mode-locked fiber laser and analyze the process of establish the mode-locked pulsein detail.The several mainly methods of passively mode-locked have been summarized in this paper,and their quality performance have been discussed in detail.(3)We have proposed and experimentally demonstrated a figure eight fiber laser(F8L)based on power imbalanced nonlinear optical loop mirror(NOLM).The Nonlinear Schrodinger equation(NLSE)and Ginzburg Landau equation(GLE)have been considered to establish the model of optical pulse propagating in the fiber and gain fiber,the Split step Fourier method(SSFM)has been used for solving the equations.We have discussed the characteristic of saturable absorber(SA)of the power imbalanced NOLM and some parameters such as nonlinear parameter,dispersion,attenuate parameter of attenuator and output ratio of optical coupler have been discussed.We have also researched the proposed passively mode-locked fiberlaser's characteristic of the output as well as the change of the output ratio that influenced the signal to noise ratio(SNR).(4)We have proposed and experimentally shown a bidirectional erbium-doped fiber laser delivering dispersion-managed soliton(DMS)and Q-switched pulse based on a graphene-polyvinyl alcohol(PVA)and nonlinear optical loop mirror(NOLM)SAs.In proposed structure,the functions of two kinds of traditional fiber laser are integrated in this pulse fiber laser.We have confirmed the three operate status.The three situations are as follows: DMS is established only,Q-switched is established only and the DMS and Q-switched are established simultaneously.To the best of our knowledge,it is the first time that Q-switched pulse and DMS have been acquired respectively or simultaneously in a fiber laser.We have investigated the relationship between the launched pump power and the output power of Q-switched pulse,as well as the full width at half maximum(FWHM)of Q-switched pulse,further more repetition frequency of Q-switched pulse and energy of Q-switched pulse have also been investigated.(5)We have generalized the whole work of this degree thesis,and have prospected for future work in this field.