自离化等离子体中激光拉曼放大机制的理论与模拟研究

项目名称： 自离化等离子体中激光拉曼放大机制的理论与模拟研究

项目编号： No.11305157

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 数理科学和化学

项目作者： 张智猛

作者单位： 中国工程物理研究院激光聚变研究中心

项目金额： 27万元

中文摘要： 激光拉曼散射放大机制通过等离子体中的向后拉曼散射效应来实现超高功率激光脉冲的压缩和放大。但是，泵浦激光穿过等离子体时会提前导致热噪声的拉曼不稳定性增长并损耗能量，限制了这种机制的实际应用。为了克服这个缺点，Malkin于2001年提出自离化等离子体中的拉曼放大概念。它以气体为媒介，让泵浦激光强度低于气体的离化阈值，避免产生等离子体而发生不稳定性。而种子激光则强到足以离化气体形成等离子体，进而实现放大。本申请项目将对这种自离化等离子体中的激光拉曼放大机制进行系统的理论和模拟研究，特别是发展包含离化过程的物理模型来理解离化与三波作用的耦合，以及发展对应的一、二维粒子模拟程序。输出激光的饱和强度和能量转换效率是激光放大技术中的两个关键参数。本项目旨在理解自离化拉曼放大的内在物理机制，寻找合适的激光、等离子体参数以及探索一些新的方法来提高两个关键参数，进而推动该机制的技术实现。

中文关键词： 激光拉曼放大；粒子模拟；波破效应；激光啁啾；包络匹配

英文摘要： The compression and amplification of laser at high power might be achieved by backward Raman scattering in plasma. One critical issue, however, is that when the pump passed through the plasma, it may be unacceptably depleted due to spontaneous Raman backscatter from the thermal noises. This limits the practical application of laser Raman amplification. Fortunately,the limitation can be overcomed by using self-ionizing plasma as proposed by Malkin in 2001. In the so-called self-ionizing laser Raman amplification mechanism, a gaseous medium is adopted with pump intensities too low to ionize the medium and the intense seed to produce plasma via rapid photonionization as it is being Raman amplified. In the current application project we will carry out systematic theory and simulation studies on this new Raman laser amplification mechanism. In particular, we will develope the theory model including photonionization to understand the coupling of ionization and three waves interaction.The 1D and 2D Particle-In-Cell codes,which can simulate the new mechanism, are also expected to be developed. It is noted that in laser amplification technology, the saturation intensity of output laser and total energy conversion efficiency are key parameters. Therefore, we will focus our research on looking for optimal regime of laser a

英文关键词： backward Raman amplification；Particle-in-Cell simulation；wave-breaking effect；chirped laser；envelope matching