Abstract Laser induced breakdown spectroscopy (LIBS) based on femtosecond laser pulses has widely been used for analyzing chemical elements in samples. In this research, we achieved the double-pulse operation with a two-polarizer configuration, and the signal enhancement factor of 4–15 was observed as compared with the single pulse LIBS scheme. It is found that with the change in interpulse delay time between 0 and 150 ps, the laser-fluence dependence of the LIBS signal enhancement can be classified into three types that are characterized by the different behavior of linear and quadratic intensity increase, followed by the intensity saturation. Such different responses are presumably ascribable to the mechanisms of electron-ion relaxation and plasma reheating. Also, different behavior is seen for the signal enhancement with different laser intensity and beam diameter while the laser fluence is kept constant. This indicates that generally, the use of a larger beam diameter is recommended for increasing the signal enhancement factor.

中文翻译：

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飞秒双脉冲激光诱导击穿光谱中信号增强的激光通量依赖性

摘要 基于飞秒激光脉冲的激光诱导击穿光谱（LIBS）已广泛用于分析样品中的化学元素。在这项研究中，我们使用双偏振器配置实现了双脉冲操作，与单脉冲 LIBS 方案相比，观察到 4-15 的信号增强因子。研究发现，随着脉冲间延迟时间在 0 到 150 ps 之间的变化，LIBS 信号增强的激光通量依赖性可分为三种类型，其特征是强度增加的线性和二次方的行为不同，其次是强度饱和。这种不同的反应可能归因于电子-离子弛豫和等离子体再加热的机制。还，在激光能量密度保持恒定的情况下，对于不同激光强度和光束直径的信号增强，可以看到不同的行为。这表明通常建议使用更大的光束直径来增加信号增强因子。