Research Of Key Technology About Compression And Stretch Of Ultroshort Pulses

Fiber as a transfer medium has two characteristics about its transmission: one is the fiber loss, and the other is fiber' s dispersion. The problem of fiber' s losses is resolved because of the appearance of Yb'i+-doped fiber amplifier in the YbH~doped ultrashort pulse fiber laser system. At the same time, the effect of dispersion accumulation and nonlinear optics affection accumulate people' s study on technology of dispersion compensation and nonlinear optics affection. Dispersion became a key factor which lead if the ultrashort pulse can be output or not in fiber laser. So, it is becomes a important question that how to compensate the dispersion accumulation in fiber laser. In this paper, the basic dispersion theory, the importance of dispersion compensation, the basic conception about dispersion and the reason of dispersion generation in Yb'^-doped ultrashort pulse fiber laser is studied experimentally and theoretically. At the same time, the mechanism of dispersion compensation and familiar ways about dispersion compensation is introduced.On the basis of dispersion theory and our requirement to the dispersion compensation, the theory of dispersion compensation and generation of higher-order dispersion and it' s compensation are studied. Numerical simulation about gratings dispersion compensate is discussed in our systems in detail. The basic structure and theory of compressor, relative parameter and etc. are mentioned in this paper.Experiments of compress working about figure-of-loop with compressor is out of the cavity and figure-of-eight with compressor is in the cavity is studied. Finally, through the optimization of the distance which is placed 28.6cm between the gratings in Ybi+-doped fiber laser, we achieved pulse duration 180fs and repetition rate 24MHz, pulse duration 307fs and repetition rate 25. 5MHz mode-locked pulse sequenceoutput in figure-of-eight fiber laser and in figure-of-loop one when a signal pulse duration 46ps is introduced . The result of Experiments is consistent with theory basically.Then the stretcher with bigger stretched ratio is designed in OPCPA system. The theory and optimized design of a kind of Offner stretcher is presented. After stimulated numerically and calculated with Matlab assistanted program based on ray-tracing, the direct graph about parameter related with stretched capability of the stretcher is gained. Analysing and discussing that how these parameters affect the stretching capability, the optimized parameter in OPCPA stretcher is presented, the results show that the stretcher in this paper can stretch 30fs pulse to 900ps.Using the optimized parameter of Offner stretcher, we did some experiments to verify our theory about strecher. we achieved pulse duration 545ps, output power 42mw and repetition rate 80MHz stretched pulse sequence when a pulse duration 30fs, input power 430mw mode-locked pulse is introduced into our stretched system in the experiment. Finally, the difference between theory and our experiment is analyzed. The results show that our theory and design about stretcher is correct basically and that the paper has important direct role to stretcher with bigger stretched ratio.