Research On The Compression Properties For Generating SBS Pulse Of Hundreds Picosecond

Nowadays the energy resources are becoming a problem to be solved. TheInertial Confinement Fusion (ICF) is a potential method to solve that contradictionradically. The shock-ignition is a way to achieve ignition proposed recently. Butthe shock-ignition needs high-energy hundred picoseconds laser pulse. Thestimulated Brillouin scattering (SBS) which not only has advantage in simplestructure, low-costing, high efficiency energy conversion and high pulse widthcompression ratio but also can improve the quality of laser beam with theconjugation property which can supply the laser pulse. This article investigates theeffect of the parameters of pump, structure and the SBS medium on the SBS pulsecompression properties such as compressed pulse width, SBS efficiency energyconversion and stability of Stokes pulse wave shape by means of theoreticalanalysis and experimental validation. Finally, new SBS mediums which makethem good candidates for generating hundred-picosecond pulse will be given out.Firstly, the Maxwell equations and Navier-Stokes equation including thesecond-order time differential of acoustic field are used to setup the SBS pulsecompression model on the one-dimensional transient condition. By using thediscretization method, the iterative scheme of the optical field and acoustic field isalso displayed. The distribution calculation model of the effect on the SBShundred-picosecond pulse compression properties is achieved and the stability ofmodel is discussed.And then through the calculation model we stimulate the effect of theparameters of pump, structure and the SBS medium on the Stokes compressedpulse width and SBS efficiency energy conversion in the SBS process. Judgingfrom the simulation results, the parameters of pump and structure have optimumvalues for one medium. However, for the different mediums, as the phononlifetime is larger (typically greater than0.6ns), the phonon lifetime plays leadingrole on Stokes pulse width. On the contrary, the phonon lifetime to gain coefficientratio would play an important role and the smaller the ratio is, the narrower theStokes pulse is. Then new mediums with the properties of lower absorption, higheroptical loads, shorter phonon lifetime and appropriate gain coefficient are foundby means of the analysis of the chemical structures and SBS properties. The SBSparameters are obtained by measuring or computing. At last, combining the simulated result three perfluorinated compoundsFC-43, FC-70and FC-770are used in experiment for the research on the SBSpulse compression properties such as compressed pulse width, SBS efficiencyenergy conversion and stability of Stokes pulse wave shape in a compact two-cellSBS system. The experimental results show that FC-70can give the shortest andthe most stable compression pulses under the same conditions. The energyreflectivity of the three mediums can all reach80%or more if the lost inexperiment is ignored. From this view, FC-70is more suitable to be chosen forgenerating SBS hundred-picosecond pulses.