相对传播的双脉冲激光与薄膜靶作用产生的强单色谐波

Strong monochromatic harmonics generated by the interaction of two counter-propagating pulses with a foil target

研究了相对传播的双脉冲激光与薄膜靶的作用,观察到很强的谐波产生.其物理图像是:圆偏振高对比度强激光脉冲作用于薄膜靶,由光压推动产生的高密度等离子体靶向前运动,同时由于电荷分离场的作用,使得离子束和电子束在纵向上都有好的聚束,从而产生以相对论速度向前运动的等离子体镜;反向入射一个探测光到已被加速的等离子体镜上,由多普勒频移产生强的单色N次谐波,探测光脉冲被"压缩"至原来的1/N.还讨论了激光和等离子体参数对等离子体镜的运动和谐波级次的影响,以及相对论运动等离子体镜的稳定性对谐波的影响.

This paper studies the strong harmonic generation in the interaction of two conter-propagating pulses with a foil target. When the thin target is irradiated by high-contrast circularly polarized laser pulse, the light pressure push high-density plasma forward. At the same time, because of the role of charge separation field, the ion beam and electron beam bunch well in longitudinal direction, and generate the plasma mirror with a forward movement at relativistic speed. When incidenting on a probe laser pulse on the plasma mirror in the opposite direction, they produce strong monochromatic N-order harmonics by Doppler shift, with the new duration of pulses compressed to 1/N of the original ones. This paper also discusses the effect of the laser and plasma parameters on plasma mirror movement which influences the order of harmonics, and also the effect of the stability of the relativistic plasma mirror on the harmonics.