Characteristics Of Dissipative Soliton Fiber Laser

The single pulse energy is an important indicator of passively mode-locked fiber lasers. Various programs and structures have been proposed to improve the energy of mode-locked optical pulse. In recent years, the dissipative soliton mode-locked fiber lasers operated in the normal dispersion regime have attracted great interest of researchers. The dissipative solitons show quite different pulse forming mechanism and physical characteristics from other conventional solitons. It can break through the energy limit of traditional solitons without wave breaking, and achieve higher energy of mode-locked pulse output. Therefore, it is of great scientific and practical importance to study on dissipative soliton fiber lasers.The main contents and results of this dissertation are as follows:Firstly, a normal-dispersion erbium-dopped mode-locked fiber laser is constructed by using the NPR technique. Stable dissipative solition pulses with central wavelength, spectral width, pulse duration, and repetition rate of 1570.1 nm, 22 nm, 4.48 ps, and 2.322 MHz are obtained, and the dissipative soliton is highly chirped. By adjusting the pump power and the state of polarization, dissipative solitons with modulation instability induced sidebands on spectrum are observed, and by using the relations between the characteristics of modulation instability induced sidebands and the dispersion, the net cavity dispersion is calculated. Besides, harmonic mode-locked dissipative soliton pulses with orders from 2th to 7th are obtained with an optimized cavity setup. The physical mechanism of harmonic mode-locked dissipative soliton pulses is also been analyzed. In addition, the bound state dissipative solitons are observed.Secondly, in the numerical calculation, a “pulse tracing” method is adopted to simulate the characteristics of dissipative solitons in a NPR mode-locked fiber laser with normal cavity dispersion. The formation and evolution process of dissipative solitons within the cavity are numerically simulated, the characteristics of polarization evolution are analyzed, the effect of the fiber gain coefficient, the linear birefringence, and the net dispersion to the laser operating state are also discussed. In addition, the process of a dissipative soliton pulse compression in the single-mode fiber outside the cavity has been numerically simulated. By optimizing the fiber length, the dissipative soliton pulse with pulse duration of picosecond order of magnitude is compressed to 370 fs.Thirdly, the characteristics of vector dissipative solitons in a graphene mode-locked fiber laser with normal cavity dispersion are numerically simulated. By adjusting the linear birefringence within the cavity, the polarization-locked vector dissipative solitons with different polarization rotation cycle are obtained, the polarization evolution process of polarization-locked vector dissipative solitons within the cavity is studied, and the comparison analysis with reported study results has also been done. Finally, by changing the small signal gain coefficient and linear birefringence within the cavity, the polarization-locked vector dissipative solitons are obtained. Further studies have shown that the polarization-rotation-locked and polarization-locked vector dissipative solitons are formed by the combined effect of linear birefringence and nonlinear birefringence within the cavity.