Studies On Ultrashort Pulse Er～(3+)-doped Fiber Lasers

Ultrashort pulse fiber lasers, which have a number of characteristics, such as closed-form waveguide structure, miniaturization, solidification, freedom from cooling and adjustment, compact configuration and low cost, is the best choice for ultrashort technology applications. It plays an important role in many fields, such as ultrashort optics, ultrashort biology, ultrashort spectroscopy, fiber communication. In recent years, the Er³⁺-doped fiber, with the widely application and fast developing of the fiber communication system has been considered as an extremely attractive medium for the generation and the amplification of ultrashort pulse and more and more researchers pay attention to it. The main content of the dissertation is the theoretical and experimental studies of the generation of ultrashort pulse in Er³⁺-doped fiber ring cavity lasers and ultrashort pulse fiber laser with SESAM.The main research works and innovations of this thesis are summarized as follows:1. A review of the research state and the potential applications of the rare-earth-doped fiber laser development history, the newest achievement, the classification, the merits and shortcomings and also the application of the mode-locked fiber laser. Some important concept about the fiber laser and principle of the mode-locked were expatiated. The producing technique of ultrashort pulse with saturation absorber, NPR and nonlinear optical loop mirror were presented. Especially the principle of NPR is discussed in detail.2. The experimental study of the generation of ultrashort pulse by stretch pulse structure cavity is carried out. By reasonably design and incorporate positive dispersive fiber, the stretched-pulses additive pulse mode-locking structure was presented. The stable mode-locked optical pulses with spectral width of 40nm, and pulse duration of about 175fs at a 33MHz repetition rate was obtained successfully by using stretched-pulses additive pulse mode-locking technique from the ring cavity fiber laser. The self-starting pump power threshold is 90mW (less than soliton fiber laser)3. The experimental study of the generation of ultrashort pulse by SESAM in fiber laser at 1550nm is carried out. The principle about passive mode-locked with SESAM is present. In the experiment, four different parameter SESAM are used in the cavity, three status: mode-locked, Q-switch and Q-switch-mode-locked are achieved. The results are discussed in detail. The stable mode-locked optical pulses with spectral width of 6nm, duration of about 137ps was obtained by using F-P cavity. The Q-switch and Q-switch-mode-locked state are also achieve in the same configuration.4. The experimental of new cavity composed with SESAM and NALM is also carried out. By incorporate the DCF fiber in the cavity, Mode-locking pulses as short as 182fs were obtained, the spectrum is 38nm, average power is 10mW, single pulse energy is reach to 0.37nJ.