Study On Propagation Properties Of Chirped-pulse In Ultra-short Pulse Amplification System

In the process of propagation in ultra-short pulse amplification system, the chirped-pulse will not only be amplified in its energy, but also be influenced by the effects of gain narrowing, gain saturation, self-phase modulation and dispersion, leading to the distortion of the temporal profile and spectrum distribution of the output pulse, resulting in the influence on the amplification, compression and beam quality of the pulse. In order to avoid the influence of the above effects, it is necessary to study the propagation and amplification properties of chirped-pulse in the chirped-pulse amplification system, as well as the inverse problem of the propagation and amplification of chirped-pulse in ultra-short pulse amplification system, so as to provide theoretical reference for the optimal design of the ultra-short pulse amplification system.In this thesis, the propagation and amplification properties of chirped-pulse in ultra-short pulse amplification system have been studied theoretically. The main results obtained in this thesis can be summarized as follows:1. Starting from the classic Maxwell's equations, the theoretical model for the study of the propagation and amplification of chirped-pulse, i.e., the nonlinear Schredinger equation, has been given. The principle of the split-step Fourier method has been introduced. By using the nonlinear Schrodinger equation and the split-step Fourier method, the effects of the dispersion, self-phase modulation, gain narrowing and gain saturation on the propagation properties of chirped-pulse have been simulated and analyzed.2. According to the different characteristics of Nd:glass and Ti:Sapphire amplification medium, the effects of Nd:glass and Ti:Sapphire amplificationmedium on the propagation and amplification properties of chirped-pulse have been analyzed in detail.3. The model of wavefront phase perturbation has been built up, where the random phase screen characterized by RMS Gradient and the random phase perturbation have been introduced to describe the low and the high frequency phase noise, respectively. Starting from the nonlinear Schrodinger equation model and using the split-step Fourier method, the influence of the wavefront phase perturbation on the spatial and temporal characteristics of chirped-pulse has been discussed in detail.4. By using the nonlinear Schrodinger equation, the split-step Fourier method and the numerical iteration method, the inverse problem of the chirped-pulse through Ti: Sapphire amplifier has been studied, in which the effects of gain narrowing, gain saturation are considered. The results would be useful for the pulse shaping of the ultra-short pulse.