Research On Passively Mode-locked Erbium-doped Fiber Laser Based On SESAM

Fiber lasers is widely used in the optical communication, sensing, aerospace, military and other fields, which is low threshold, high power, good reliability, compact structure, good heat dissipation, and many other advantages. In recent years, as a kind of stably and reliably ultrashort pulse laser light source, ultrashort pulse passively mode-locked fiber laser develops fast. Based on the optical nonlinear effect to achieve mode-locked, its laser cavity has no any active devices. The passively mode-locked erbium-doped fiber laser for semiconductor saturable absorber mirror, in recent years, becomes the ultrashort pulse mode-locked fiber laser research hotspot and has very wide application prospect, which has the advantages of small size, high stability, self-start and so on.This thesis mainly outspreads the study in focusing on the passively mode-locked fiber laser for SESAM to achieve ultrashort pulse. In the article, build the mathematical model of the passively mode-locked fiber laser based on SESAM, implement the numerical simulation of the mode-locked Erbium-doped fiber laser system by using split-step Fourier method(SSFM), set up the experimental system of passively mode-locked fiber laser and achieve the mode-locked output, and analyse simulation results and the experimental results. At the same time, study the parameter influence of pump power, dispersion and other factors on the passively mode-locked erbium-doped fiber laser. Main jobs:1. Analyze the main structure of passively mode-locked fiber laser and its development. Compare the advantages and disadvantages of several structures. Introduce the development status of passive mode-locked fiber laser based on SESAM in recent years. Describe SESAM working principle, basic structure and main characteristic parameters.2. Deduce the nonlinear Schrodinger equation and numerical method of light transmission characteristic in the optical fiber. From the rate equation of erbium-doped fiber amplifier (EDFA), establish the numerical model of optical signal transmission within erbium-doped fiber by the step traveling wave method. On this basis, establish the totally numerical analysis model and the corresponding numerical simulation program of passively mode-locked fiber laser based on SESAM.3. By using the established numerical simulation program, more thorough and comprehensive numerical simulation of passive mode-locked fiber laser based on SESAM is studied. In addition, study the change of spectrum width and pulse width with pump power, dispersion, loss and other factors.4. Set up the experimental system of passively mode-locked fiber laser. Realize the stability mode-locked laser output, and the repetition frequency is13.7MHz. In experiment, study spectral characteristics of mode-locked laser output under the condition of different pump. As a result of the limitation of experimental conditions, the experiment fails to observe real mode-locked pulse waveform and pulse width. According to the output spectrum, estimated value of mode-locked pulse width is about0.8ps.