Theoretical And Experimental Study On Er-Yb Co-doped Passively Mode-locked Fiber Laser

Nowadays, the generation of ultrashort laser pulse is an active research front in nonlinear optics and ultrafast optics. Comparing with semiconductor lasers, the fiber lasers with rare-earth-element fiber as gain medium possess good gain features, high conversion eficiency, low threshold, high beam quality, and compatibility with fiber-optic communication system. It has already become one of the hottest topics in the field of ultrashort pulse laser research. On the basis of our laboratory facilities, we focused on mode-locked Er-Yb co-doped fiber laser and make the following work theoretically and experimentally.I. The basic theory of the fiber laser1. The basic principles, history, classification and characteristics of the fiber laser is firstly introduced. We also discussed the development and significance of the ultrashort pulse fiber laser.2. The characteristics of the Er-Yb co-doped fiber laser is telled, then we referred to the phenomenon of Er3+ ions quenching when the concentration of Er3+ ions is higher is suppressed effectively by adding the Yb3+ ions. We also introduced the research process of the Er-Yb co-doped ultrashort fiber laser.II. The principle of the mode-locked fiber laser and the theory of Er-Yb co-doped fiber laser.1. The mechanism of mode-locking in fiber laser was investigated, including active, passive and active-passive mode-locked.2. Introduced theory of the Er-Yb co-doped fiber laser, then through maths expressions we analyzed the dependence of output character on length of doped fiber, pump power, slope efficiency and threshold value and gived the relation of them by simulated numerically.III. Experiment study of nonlinear polarization rotation mode-locked Er-Yb co-doped fiber laser1. Introducing three kinds of passive mode-locked fiber laser in details, then we studied the nonlinear polarization rotation mode-locked with emphasis. Starting from the time-domain mode-locking master equation, we analyzed the the mechanism of additive pulse mode-locking of equivalent fast saturable absorber and fully discussed the influences of bandwidth, cavity losses, dispersion on the fiber laser.2. Exploiting the nonlinear polarization rotation technique and adjusting the polarization controllers'orientations and pump power, we achieved stable operations of Q-switched, Q-switched mode-locked and CW mode-locked regimes in a ring cavity Er-Yb co-doped fiber laser and make a detailed record of the repetition rate, pulse width, spectrum width, output power dependence on pump power.