超强脉冲激光在低密度等离子体中的相对论自导引效应

Relativistic Self-Guiding of Ultrashort Laser Pulse Radiation in Low Density Plasmas

分析了相对论条件下激光超短脉冲在等离子体中的传输特性 ,在傍轴近似和慢变振幅近似条件下 ,推导了折射率、电子密度、静电场以及电子空腔尺度的表达式。当激光功率超过产生自导引阈值功率时 ,激光束斑沿着传输光轴方向振荡。在有质动力产生的压力非常强时 ,聚焦光束中央部分的电子被全部排开形成电子空腔。给出了电子空腔的尺寸以及在出现电子空腔时的处理方法。在超过形成电子空腔的阈值功率 (Pc≈ 2 .5TW )时 ,空腔的尺度几乎与激光功率无关 ,这意味着电子空腔阻止了激光脉冲的进一步聚焦。

The propagation characteristics of ultrashort high-power laser pulses through low density plasmas is analyzed by considering relativistic effects. The expresssions of refractive index, electron density, electrostatic field and the dimension of electron cavity are derived. For laser power exceeding the dritical power of self-guiding, self-guiding occurs and laser beam oscillates along the propagation direction. For the laser power exceeding the critical power (P c≈2.5 TW) of the electron cavitation, electron cavity occurs. The expression of the electron cavity dimension is presented. With the laser power increasing, cavity dimensions are almost independent to the laser power, which implies that the electron cavity prevents the further focusing of the laser pulses.