Studies On Figure-of-eight Cavity Yb～(3+)-doped Fiber Lasers

Fiber lasers with laser diode pumping are appealing alternatives to bulk solid-state lasers, owing to their inherited outstanding properties compared to the common solid state lasers, such as compact configuration, freedom from cooling and adjustment. Rare earth doped silica fibers have been used for many years to create continuous wave lasers. And Er-doped fiber amplifiers are now widely used in telecommunications. Ultra-short pulse laser system based on fiber lasers and amplifiers are the best choice for ultra-short technology applications because they are mini-atomization, freedom from cooling, compact and low cost. With its broad gain bandwidth and high optical conversion efficiency, Yb-doped silica fiber represents an attractive medium for the generation and amplification of high-energy ultra-short optical pulses in recent years. More and more researchers pay attention to it.The main research works and innovations of this thesis are summarized as follows:1. The experiment of the single mode Yb³⁺-doped fiber amplifiers and gratings compressor was discussed. The seed pulses come from a mode-locked Yb-doped figure-of-eight cavity fiber laser. The experimental study of the Yb-doped figure-of-eight cavity fiber laser using the nonlinear amplifying loop mirror (NALM) was done. The fiber laser can generate 0.2mW average power of 43.6ps pulse duration at a repetition of 18.2MHz, and operating central wavelength was 1053.3 nm, spectrum width was 8 nm, though grating pairs to compensate the positive dispersion outside the cavity, as short as 616 fs output pulse was obtained after amplifying.2. Polarizing related Isolators and maintaining fiber coupler, the use of intracavity polarization maintaining fiber, nonlinear amplified loop mirror figure-of-eight cavity mode-locked laser pulse was high extinction ratio of pulse mode-locked laser output repetition frequency of 13.46 MHz, extinction ratio higher than 25 dB. When the operating center wavelength was 1057nm, 108.8 ps pulse was obtained, and generate 1.87mW average power.3. The experimental study of Yb³⁺-doped fiber lasers using the manual tunable fiber Bragg grating for wavelength continuous tuning mode-locked operating was reported. In the experiments, we observed by adjusting tunable fiber grating filter, the fiber laser was self-starting easily and the operating center wavelength could be tuned from 1047nm to 1055nm, pulse duration at a repetition rate of 4.9MHz. The fiber laser could generate 8.02mW average power of 259.3ps when the operating center wavelength was 1051nm and spectrum width was about 1nm.4. A detail investigation about this phenomenon is present in this paper. Analyzing the process of the mode-locking in the cavity, we discover the noise in the cavity affect the mode-locking starting process of the fiber laser. It was experimented that the mode-locking starting is achieved more quickly by injecting pulses noise into figure-of-eight Yb³⁺-doped fiber laser.