通过对飞秒激光在空气中产生的等离子体通道两端外加高压,来研究通道的寿命变化情况。实验得到,当在等离子体通道两端外加高压时(350 kV/m),等离子体通道寿命延长了近3倍。理论模拟和分析结果表明在外加电场条件下,碰撞电离得到增强,吸附作用相对减弱,解离复合系数随着电子平均能量的增加而下降的趋势更为剧烈,这进一步引起了等离子体通道寿命的延长。实验结果与理论分析共同表明了利用外加电场对空气中激光等离子体通道寿命进行延长的可行性。

The lifetime of plasma channel induced by femtosecond laser in air is investigated by adding external high voltage electric field. The lifetime is extended three times when the voltage reaches 350kV/m in our experiment. Theoretical simulation and analysis show that impact ionization is enhanced and attachment effect is reduced in high-voltage electric field. Also, a sharper falloff in dissociative recombination rate will lead to a corresponding marked increase in the lifetime of the plasma channel. Both experimental and theoretical results prove the feasibility of adding external electric field in prolonging the lifetime of plasma channel in air.