Quantitative measurement of electron number in nanosecond and picosecond laser-induced air breakdown
Quantitative measurement of electron number in nanosecond and picosecond laser-induced air breakdown
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纳秒和皮秒激光诱导空气击穿中电子数的定量测量
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
Zhili Zhang
中科院分区：
文献类型：
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作者：
Yue Wu;J. Sawyer;L. Su;Zhili Zhang
在这里，我们提出了定量测量的总电子数在激光诱导的空气击穿的压力范围从大气压到40 barg的10 ns和100 ps的激光脉冲。激光诱导击穿阈值的一个可量化的定义是通过介电校准的相干微波散射的可测量的总电子数急剧增加。对于10 ns的激光脉冲，大气中的激光诱导击穿阈值被定义为总电子数为106。该击穿阈值随压力和激光光子能量（较短波长）的增加而减小，这与初始多光子电离和随后的雪崩过程的理论一致。对于100 ps的激光脉冲的情况下，一个明确的阈值是不存在的，只能观察到边缘的压力效应，这是由于短的脉冲持续时间导致更强的多光子电离和最小的碰撞雪崩电离。
Here we present quantitative measurements of total electron numbers in laser-induced air breakdown at pressures ranging from atmospheric to 40 barg by 10 ns and 100 ps laser pulses. A quantifiable definition for the laser-induced breakdown threshold is identified by a sharp increase in the measurable total electron numbers via dielectric-calibrated coherent microwave scattering. For the 10 ns laser pulse, the threshold of laser-induced breakdown in atmospheric air is defined as the total electron number of ∼106. This breakdown threshold decreases with an increase of pressure and laser photon energy (shorter wavelength), which is consistent with the theory of initial multiphoton ionization and subsequent avalanche processes. For the 100 ps laser pulse cases, a clear threshold is not present and only marginal pressure effects can be observed, which is due to the short pulse duration leading to stronger multiphoton ionization and minimal collisional avalanche ionization.