Studies On High-power Self-similar Er-doped Fiber Amplifier

THz radiation has a broad application prospect in many areas. There are many ways most of which need high-power ultra-short pulses as excitation source to generate the THz radiation. The application in this area improves the status and essentiality of the ultra-short pulse laser.Among different ways of generating short pulse, fiber amplifier is the most popular one for its simple structure, high efficiency and stability. Self-similar amplification system takes people's attention in the last few years because it can broaden the spectrum of the pulse along with energy amplification. it is helpful to get high power ultra-short pluses. The most important factors which limit the self-similar system are the finite gain bandwidth and the Stimulated Raman Scattering(SRS).Focus on the effect, this text finished the study of Er-doped self-similar system, and give the precept of designing the system.The main work summarized as follows:1. We summarized the theory and development of many methods for generating ultra-short pulses. After comparing the characteristics of different systems deeply and detailedly we point out the advantage of self-similar amplification system.2. The analysis of pumping scheme showed that it is possible to carry out uniform pump in a wide rang of gain coefficients in the self-similar system by matching the forward and backward pump power.3. We studied the theory and effect of the finite gain bandwidth and the Stimulated Raman Scattering(SRS)proceed in the self-similar amplification system. By predigesting the analysis and calculation, we give the threshold value to avoid the disadvantageous factors.4. After discussing the effect of SRS and finite gain bandwidth respectively, we study the uniformity of gain coefficient.4. Focus on the Er-doped fiber and seed pulse in our laboratory, by adjust the gain coefficient and the length of Er-doped fiber, we simulated different self-similar amplification systems. The results showed that below the threshold value, the largest output energy of the system is 16.0 nJ, and we calculated the length of fiber and gain coefficient when the largest power was got.5. One the one hand, by studying the effect of the seed pulse input in the self-similar amplification system, we found that the largest energy we can get from the self-similar amplification systems has nothing to do with the energy of the seed pulse. On the other hand by changing the parameter of the fiber in the system, we found that larger dispersive and smaller nonlinear coefficient were propitious to get higher power.