Research On The Propagation Properties Of Ultra-short Pulse In Optical-fiber Laser

This thesis, based on a full study of background and development for self-similar pulse, gives a simple introduction of the basic mathematics model about pulse transmission in the optical fiber amplifier. This model includes the nonlinear Schrodinger equation and the Ginzburg-Landau equation. And we importantly discuss the impacts of gain dispersion and two-photon absorption on self-similar pulse, the linear relationship between the two parameters, and their interval graph. Also we study the impacts of linear gain on self-similar pulse propagation, as well as the interval graph of the two parameters. It is found that as long as selecting the parameters appropriately, arbitrary initial input pulses can evolve into self-similar pulses in the fiber amplifier with gain saturation, gain dispersion, third-order dispersion, self-frequency shift and self-steepening effect. When selecting the parameters ε, χ or δ, χ within certain intervals, we can describe the central region of the self-similar pulse with the invert parabola; What’s more, the parameters ε, χ or δ, χ are approximately linear, and the size and growth rate of the pulse power, the width, peak amplitude and the pulse intensity will change with the parameters. Thus, choosing the parameters reasonably, in the fiber amplifier, is very important for us to obtain the proper self-similar pulse.