The Research On All-normal-dispersion Mode-locked Yb-doped Fiber Laser

Mode-locked Yb-doped fiber lasers are being used in different areas, including optical frequency metrology, material processing, terahertz generation, and so on. Historically, major advances in laser performance have always followed the discovery of new mode-locking regime. Therefore, there is always a intensive motivation to explore new mode-locking regimes. All-normal-dispersion mode-locked Yb-doped fiber laser can generate high-power and high-linear-chirp dissipative soliton pulses. The generation of dissipative solitons is contributed to an integrated result of all kinds of effects in laser cavity, such as gain, loss, gain saturation, nonlinear effects and filtering.In this thesis, all-normal-dispersion Yb-doped fiber laser is the research object. Firstly, we found several different operating modes in the all-normal-dispersion Yb-doped laser experimentally, and explained them theoretically.In further research, we added a bandpass filter into the fiber laser, and mainly focused on theoretical research and numerical simulation. The filtering effect on the performance of output dissipative soliton pulses has been detailedly investigated. Numerical simulation showed that dissipative solitons obtained in the fiber lasers with band-pass filter has narrower pulse duration and broader spectrum width than those from the lasers without filter. Moreover, the establishing time of stable mode locking is shorter. The peak power of dissipative soliton pulses increase with the filter bandwidth decreasing, while pulse energy almost keeps invariable within certain range of filter bandwidth. But in the limiting case of narrow filter bandwidth, the pulse energy decreases abruptly due to the induced large loss.At last, we utilized a periodic birefringence fiber filter in the all-normal dispersion mode-locked Yb-doped fiber laser. In experiment, we obtained dual-wavelength mode-locked disspative solitons from this all-normal-dispersion Yb-doped fiber laser. In simulation, multi-wavelength dissipative solitons could be generated by adding a filter into the fiber laser. And adjusting the bandwidth of filter, multi-wavelength dissipative solitons with different wavelength number and separation could be generated. This is the first time to observe multi-wavelength mode-locked dissipative solitons with dissipative soliton molecules (DSM) generated from mode-locked fiber laser. Adjusting the parameters of the filter and saturation power also could change the number and wavelength of DSM in the multi-wavelength pulses.These conclusions could contribute to the generation of the high-power ultrafast dissipative soliton pulse from the all-normal-dispersion fiber laser with theory references and experimental evidences.