纳秒激光大气等离子体通道的实验研究

Experimental Study on the Plasma Channel Produced by Nanosecond Laser in Air

为研究激光击穿大气等离子体通道的长度、寿命及导电特性,应用光束整形的方法将Nd∶YAG脉冲激光2.1 J的能量均匀分布到长度约为1 m的直线上,均匀击穿大气,形成等离子体通道。从空间和时间的角度,分别研究了该等离子体通道的长度、寿命,并使用电学探测手段研究通道的连续导电性。实验结果表明,纳秒激光大气等离子体通道连续导电的空间长度可达80 cm左右,存活寿命在500 ns以上,通道的电阻主要由耦合电阻构成。这些实验结果是飞秒激光大气等离子体通道研究的有益补充,并为大气等离子体通道的应用技术开发提供了实验依据。

The length and lifetime of the plasma channel induced by nanosecond laser in air is investigated. The energy of Nd： YAG laser （pulse energy about 2. 1 J） was averaged to a straight line through beam shaping and a 1 m long plasma channel was formed by laser breakdown. The lifetime of this channel was detected with intensified charge coupled device （ICCD） and the electric continuity was studied by electrical detecting method. The experimental results indicate that the continual electric conduction spatial length of nanosecond laser induced air plasma channel can reach near 80 cm. with the survival life above 500 ns. The channel total resistance is mainly constituted of the coupling resistance. These results are helpful for researching the femtosecond laser induced plasma channel, and also provide experimental evidences for prolonging the decay time and length of laser-induced air plasma channel in technical applications.