强激光在窄通道中传播的理论研究

在考虑相对论和有质动力非线性以及全局电量守衡的前提下,分析了强激光在冷等离子体窄通道中稳定传播的情况。采用较为简化的二维理论模型,给出了描述激光和通道横向结构的解,对不同通道宽度、通道密度、激光强度和电磁模式等进行了讨论,分析了其对激光在等离子体通道中传播的影响。分析发现,在存在预通道的情况下,当等离子体通道的密度大于临界密度很多时(例如20倍临界密度),即使是在激光波长量级的通道中,激光仍然可以传播。通道越宽,等离子体密度越小;激光强度越大越容易传播。在同样的通道和传输情况下,TE0模传输所需要的激光强度比TE1模要小。

Theoretical Studies on Propagation of Ultraintense Laser Pulses in Preformed Narrow Plasma Channel

The steady propagation of an ultraintense laser pulse in a preformed narrow plasmas channel with the width in the order of laser wavelength is investigated,considering relativistic and ponderomotive nonlinearities and global charge conservation.A simplified two-dimensional model is derived to describe the structures of laser pulses and the channels and exact analytical solutions describing the cross-sectional structures of the laser amplitude and plasma density are presented.The influences of the channel width,plasma density,laser intensity and mode of electromagnetic field on laser pulse propogation in the plasma channel are also discussed.It is proved that if there is a preformed channel,the laser pulse can still propagate in the channel of pulse-duration order,even if the plasma density is much higher than the critical density(e.g.20 times critical density).If the channel is wider,the plasma density is lower and when the laser intensity is higher,the laser pulses will propagate more easily.In the same channel condition,a higher laser intensity is needed for TE_1 mode propogating at the same group velocity as for TE_0 mode.