利用等离子体非线性系数实现超强脉冲的压缩

High-Intensity Pulse Compression with Plasma Nonlinearity

超短脉冲压缩技术在强场物理研究中有非常重要的作用。但由于强场电离现象在惰性气体自相位调制脉冲压缩技术中限制了脉冲的能量 ,Tempea等人提出可以采用等离子体非线性系数对脉冲进行压缩。本文在考虑毛细管内表面电离的情况下 ,讨论能量为 10mJ左右、脉宽为 5 0fs的脉冲的压缩问题 ,发现可以将脉冲压缩至5fs左右。计算表明频谱展宽可以在气体密度很低的情况下进行 ,这样将可以减小电子对脉冲传播的影响。同时 ,由于毛细管内表面也处于电离状态 ,从而使脉冲能量不会受到电离阈值的限制。

Ultrashort-pulses with a duration of several optical cycles are very important in intense field physics research. 0.1 TW/5 fs laser pulses have been generated successfully. However, the high intensity ionization of medium limits the pulse energy of the self-phase modulation in single mode fiber and hollow fiber filled with noble gases. G. Tempea and T. Brebec suggested that plasma nonlinearity can be used to compress the pulse. The possibility of compressing a 50 fs pulse of about 10 mJ is investigated and the pulse compression involved in the ionization on the inner face of a hollow fiber is discussed. Based on numerical simulation, it is found that the pulse can be compressed to 5 fs in a lower density gas. So it is possible by decreasing the gas density to reduce the electron density because too much electrons will destroy pulse shape.