On the Efficiency of Parabolic Self-Similar Pulse Evolution in Fiber Amplifiers with Gain Shaping

Abstract

We numerically and experimentally demonstrate the influences of gain fiber length, initial pulse center wavelength, duration, chirp, and temporal profile for efficient parabolic self-similar evolution, accounting for the strong gain shaping effect in fiber amplifiers under high gains. A spectrally resolved numerical model allowing for realistic descriptions of the variable wavelength-dependent gain is developed. The results predict the specific regions of the initial center wavelength and the duration for the self-similar evolution, which move toward a longer center wavelength and a broader duration range with the increasing gain fiber length. For short-length high-gain amplifiers, a proper negative initial chirp can not only resist the gain-shaping deformation and facilitate the self-similar evolution but also provide a broadband output. In addition, a triangular initial profile is found to be of minimum sensitivity to the detrimental gain shaping and optimum for efficient self-similar evolution. The experimental results confirm the numerical predictions. The studies of the fast parabolic pulse formation in short-length high-gain amplifiers presented here demonstrate the potential for performance scaling of femtosecond fiber amplifiers, few-cycle pulse sources, high-power frequency combs, and related applications.