Generation and Interaction of Dissipative Solitons in Fiber Lasers

This thesis presents the study of various fiber gain materials, new laser operating regimes and pulse dynamics in mode-locked fiber lasers. Consideration was paid primarily to investigation of energy level transition in Bi-doped alumosilicate- and phosphosilicatecore fibers as promising gain media for mode-locked fiber lasers and amplifiers. The first experimental evidence of dissipative dispersion-managed soliton was obtained on basis of Tm-Ho-doped fiber laser. The role of laser cavity parameters on dissipative soliton interaction was experimentally investigated in mode-locked fiber lasers operated at different wavelengths. The energy transition in bismuth-doped alumosilicate- and phosphosilicate-core fibers was examined using the spectroscopy of transient oscillations at room and liquid-nitrogen temperatures. Bi-doped alumosilicate fiber provides luminescence at the 1.18 μm wavelength band, while Bi-doped phosphosilicate fiber emits at 1.32 μm. The study revealed three-level transition at room temperature and a four-level system at liquid-nitrogen temperature at the 1.18 μm wavelength range. The long-wavelength range, 1.32 μm, operates via four-level transition scheme at room temperature. The new mode-locked fiber laser regime was experimentally demonstrated in a Tm- Ho-doped fiber laser cavity operated at 2 μm. The dissipative dispersion-managed solitons, emitted by the laser in the normal net cavity dispersion regime, exhibited superior performance compared to dispersion-managed solitons in anomalous dispersion in the same cavity. A detailed analysis of pulse dynamics in the mode-locked fiber laser was performed. Under thorough control of the laser parameters, the different soliton groups were obtained: bound solitons, bunch of solitons, soliton rains. Parameters affecting soliton interaction include the recovery dynamics of the saturable absorber, the recovery dynamics of the gain medium, net cavity dispersion, nonlinearity, the sign of gain medium dispersion.