激光脉冲诱导的等离子体密度调制及其产生的相位反射  

Density modulation produced by ultrashort laser pulses and the phase reflection induced in underdense plasmas

作　　者：张秋菊[1] 盛政明[2] 苍宇[2] 张杰[2] 

机构地区：[1]山东师范大学物理与电子科学学院,济南250014 [2]中国科学院物理研究所光物理开放实验室,北京100080

出　　处：《物理学报》2005年第9期4217-4222,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10105014;10075075);国家高技术惯性约束聚变基金;国家重点基础研究特别基金(批准号:G1999075200)~~

摘　　要：理论研究和数值模拟发现入射光和反射光在低密度等离子体中形成的干涉场可以产生深度的等离子体密度调制.对于中等强度的入射光,譬如1015W/cm2,产生密度调制的时间尺度在几十个光周期的范围.这样的等离子体密度调制可以起类似布拉格反射镜的作用,使得后面的入射光在临界面以下的区域产生相位反射.因为密度调制的周期是光在等离子体中波长的一半,其产生的反射率可以接近100%.相位反射也可以在不均匀的低密度等离子体中产生,它可以极大地减少等离子体对光的吸收,因此在惯性约束核聚变中需要考虑到它的影响.It is shown theoretically and by particle-in-cell simulations that the interfering fields of the incident and reflected laser pulses can produce deep plasma density modulations in underdense pre-plasmas. This occurs within a few tens of laser cycles if the incident laser pulse is at moderate intensities such as 10^15W/cm^2. Such density modulations can serve as a Bragg reflector, which results in phase reflection from underdense plasmas. Because the deep density modulations are just a period of half a wavelength in the plasma,the reflected wave reaches the maximum by resonance with a reflectivity up to near 100% .The phase reflection can also be observed from the plasma with a linear density profile, which can significantly reduce the laser absorption by fusion targets.

关 键 词：相位反射 密度调制 激光等离子体 粒子模拟 低密度等离子体 密度调制 反射光 相位 激光脉冲 惯性约束核聚变 诱导 布拉格反射镜 入射光 

分 类 号：O53[理学—等离子体物理] TN123[理学—物理]