超短超强脉冲激光在空气中产生的电离通道的寿命研究

Lifetime of the plasma channel produced by ultra-short and ultra-high power laser pulse in the air

对超短超强激光脉冲在大气中传播时形成的电离通道的寿命进行了理论研究 .综合考虑了通道中自由电子 ,正离子 ,负离子的复合 ,自由电子和中性分子的吸附以及在后续激光作用下的退吸附过程 .推导出了退吸附激光强度恒定时通道中带电离子密度的速率方程的解析解 .计算结果表明 ,通过引入退吸附激光抑制电子和中性分子的吸附作用能够在微秒的时间尺度上将电子密度维持在 10 1 2 — 10 1 3cm- 3的水平 ,在相同的波长和平均功率下 。

The time evolution of plasma channel produced by ultra-short and ultra-high power laser pulses in the air has been investigated. The theoretical model considers the recombination of free electrons, positive and negative ions, as well as the attachment and detachment of electrons on neutral molecules in the air under the interaction with the successive coming laser's pulses. The analytical solution of rate equations of the charged particles in the plasma channel has been found when the detachment laser intensity is constant. Calculations show that the lifetime of the plasma channel with an electron density higher than 10^(12)—10^(13)cm^(-3) can be extended to microseconds by using a detachment laser to suppress the attachment between electrons and neutral moleculars. In the case of same wavelength and average power, the detachment efficiency of a short pulse sequence with a high repetition rate is higher than that of a continuous detachment laser.