The Research On Nonlinear Pulse Dynamics In Passively Mode-locked Fiber Lasers

Ultra-short pulse fiber lasers had been increasingly used in optical communication, optical sensing, precision machining, biomedicine, defense and military. They had become a national strategy and one of the core technologies of the industries, and also was the forefront of research topics of nonlinear optics theory. The research on the nonlinear pulse dynamics of ultra-short pulse fiber lasers caused widespread academic concerns. There were distinct characteristics of nonlinear pulse dynamics in ytterbium-doped, erbium-doped and thulium-doped fiber lasers. Pulse shaping mechanisms in passively mode-locked fiber lasers could be studied through the experiments and the numerical simulation. The generation of stable giant chirp pulse was demonstrated from passively mode-locked ytterbium-doped fiber laser with ultra-long cavity. A detailed and systematic understanding of the relationship between the dissipative mechanisms and the steady-state pulse in the ultra-long cavity fiber lasers was reported. The nonlinear pulse dynamics and the pulse-shaping mechanisms in dispersion-managed passively mode-locked erbium-doped fiber lasers were demonstrated. Stable passively semiconductor saturable absorber mirror mode-locked conventional solitons thulium-doped fiber laser was constructed, and the scheme of high-performance thulium-doped fiber laser was proposed.1. The dissipative soliton in passively mode-locked ytterbium-doped fiber lasersPulse-shaping mechanisms of the dissipative soliton in passively mode-locked ytterbium-doped fiber lasers were investigated by experiments and theoretical modeling. The dispersion-managed passively mode-locked ytterbium-doped fiber lasers were designed by using the photonic crystal fiber with negative group velocity dispersion at 1 μm wavelength. The effects of the net cavity dispersion on the pulse width and spectrum width were analyzed. The generation of the giant chirp pulse from ytterbium-doped fiber laser with the cavity of 2000 m length was demonstrated experimentally and theoretically. The Raman scattering was the main factor limiting the larger pulse energy in this configuration and enhanced the destabilization of the mode-locked ultra-long fiber lasers. The phase of the giant chirp pulse and the compensation of the frequency chirp were discussed theretically. The theoretical modeling and experimental results allowed us for a deeper insight into the inherent limitation in the ultra-long cavity fiber laser. The dissipative soliton resonance phenomenon could also be obtained in the ultra-long cavity fiber laser. With the reverse saturable absorption, the pulse width got larger when the pump power increased. The dynamics of the dissipative soliton resonance phenomenon in mode-locked ytterbium-doped fiber laser with ultra-long cavity were modeled using the extended nonlinear Schrodinger equation.2. The nonlinear pulse dynamics in passively mode-locked erbium-doped fiber lasersThe nonlinear pulse dynamics in the passively mode-locked erbium-doped fiber laser were studied through the numerical simulation and experiments. The dispersion-managed erbium-doped fiber lasers were designed by using dispersion compensation fiber with normal group velocity dispersion at 1.5 μm wavelength. The pulse shaping mechanisms and the pulse evolutions in cavity with different values of net cavity dispersion were reported. By properly adjusting parameters, dissipative solitons with distinct characteristics could be obtained from the same oscillator. The spectral filtering effect induced by the laser components was crucial for the pulse transformation. These gave us a deeper insight into the dissipative system described by the extended nonlinear schrodinger equation.3. Passively mode-locked thulium-doped fiber lasersPulse-shaping mechanisms in passively mode-locked thulium-doped fiber lasers were investigated by experiments and theoretical modeling. Stable passively semiconductor saturable absorber mirror mode-locked thulium-doped fiber laser was demonstrated, producing pulses of 712 fs width with high repetition rate of 108 MHz and high pulse energy of 0.65 n J. The generation of the dissipative soliton in dispersion-managed thulium-doped fiber laser was theoretically modeled. The distinct pulse intensity profiles evolution from the Gaussian shape to parabolic shape was reported with the spectral filtering effect. This greatly enriched the nonlinear dynamics of the thulium-doped fiber laser and the theoretical modeling supplied us reliable and attractive instruction for the high-performance thulium-doped fiber lasers.