Investigation On SBS Short Pulse Compression Based On Medium With Short Phonon Lifetime

High-energy picosecond pulses are mainly applied for ignition in laser inertial confinement fusion (ICF). Stimulated Brillouin scattering (SBS) has a characteristics of phase conjugation and pulse compression based on SBS has been widely investigated. Studies show that phonon lifetime of SBS medium is one of critical factors to determine the characteristics of SBS pulse compression. This thesis, which aims at picosond pulses obtained from the SBS pulse compression, is mainly composed of two parts: the first one is theoretical research on relationship between medium phonon lifetime and SBS pulse compression; the second one is the experimental study of SBS pulse compressions with different media.Firstly, transient model is built for simulation from SBS wave equations. The impacts of pump parameters, structural parameters and medium parameters on Stokes pulse shape are numerically simulated. The results show that all the parameters mentioned above affect the SBS pulse compression. The proper choice of media with short phonon lifetimes, optimization of pump and structural parameters are essential to the generation of picoseconds pulse.Secondly, conventional SBS media with high absorption coefficients and low power-load abilities are analyzed and the reasons behind are explained in terms of their structures. The perfluorocarbon-compound media with lifetimes below 0.5 ns, which include HT-135, HT-200, LS-210, FC-40, FC-43, FC-70, FC-5312, are reported and their gain coefficients and SBS frequency shifts are calculated.Thirdly, three perfluorinated compounds with different phonon lifetimes (FC-72,HT-135 and FC-40) are choose for the research on the impact of phonon lifetime on the pulse compression in a compact two-cell SBS system. The Stokes pulse shapes and energy conversion rate with different pump energies are obtained for different phonon lifetimes. The results show that high pulse compression ratio is obtained when SBS medium with a short phonon lifetime is choose. The results also show that absorption coefficients and optical breakdown thresholds should also be taken into consideration. Moreover, theoretical and experimental results show that the most suitable media for short pulse compression ratio are perfluorinated compounds so far.