Research On The Media For Hundred Picoseconds Pulse Compression By SBS

A new plan called impact ignition has been proposed in the Inertial ConfinementFusion (ICF), which greatly accelerates the ICF research. This plan urgently needs thehundred picoseconds laser pulse. In addition, the hundred picoseconds laser pulse hasimportant applications in many fields, such as produce of plasma, Extreme Ultra Violet(EUV) Lithography, Thomson scattering LIDAR diagnosis, laser medical treatment andso on.In this research, we mainly talk about the pulse compression technology based onthe Stimulated Brillouin Scattering (SBS). Compare to the other pulse compressiontechnologies, it can get higher compression rate, higher energy conversion efficiency,lower cost and higher amplification efficiency. Studies show that different medium isone of factors to determine the Stokes pulse width. This thesis, which aims at mediumfor the characteristics of SBS pulse compression, is mainly composed of thetheoretically and experimentally investigation. The first part provides the influence ofkinds of medium parameters on the Stokes pulse width in theory; the second part givesthe comparative study of four media with different medium parameters in experiment,and then obtain200ps of Stokes pules width or even more narrow laser pulse. As aresult of the experiment, we proposed the main SBS parameters affecting thecharacteristic of SBS pulse and found out new media as a substitute of FC-40.Firstly, the theoretical model is based on SBS pulse compression process. Bypreserving the second-order time derivative, the numerical model is built through SBSprocess, which is started by a spontaneous scattering, with a trigonometric algorithm intime and space domain and then we wrote the program code. The correctness isconfirmed by comparing with foreign papers.Secondly, we numerically simulated the influence of different medium parameterson Stokes pulse width and SBS energy conversion efficiency. Analytical work is doneby considering the changes of Stokes pulse width and acoustic field with differentmedium parameters, such as phonon lifetime, gain coefficient, refractive index andspeed of sound. In order to further analyze the priority of the four medium parameters,normalized algorithm is used and find out the main parameters of medium intheoretically.Finally, we choose four media with different parameters in a compact two-cell SBSsystem to do a comparative experiment. Preliminary work about the SBS pulsecompression characters with different structure parameters is done to ensure the stabilityof Stokes pulse. And then we obtain200ps of Stokes pules width or even more narrow laser pulse. We also study the main parameter of medium which affects the characters ofStokes pulse and confirm the correctness of theoretical work by combining thenumerical stimulation and experimental study. Two new perfluorocarbon media, FC-3283and FC-770, which have the same nature as FC-40and perfect SBS compressioncharacteristics, are found.