Optical Emission Spectroscopy Analysis of the Early Phase During Femtosecond Laser-Induced Air Breakdown

• Published in: Plasma science & technology Vol. 16; no. 9; pp. 815 - 820
• Main Author: 刘小亮 曹瑜 王小山 刘作业 郭泽钦 史彦超 孙少华 李玉红 胡碧涛
• Format: Journal Article
• Language: English
• Published: 01.09.2014
• Subjects: Delay; Density; Diagnostic systems; Femtosecond; Laser plasmas; Lasers; Optical emission spectroscopy; Temporal logic; 击穿; 发射光谱; 早期阶段; 激光诱导等离子体; 电子数密度; 空气等离子体; 超短激光脉冲; 飞秒激光脉冲
• ISSN: 1009-0630
• DOI: 10.1088/1009-0630/16/9/02

Single-pulse and double-pulse optical emission spectroscopy （OES） analyses were carried out in air by using ultrashort laser pulses at atmospheric pressure. The aim of this work is to use spectroscopic methods to analyze the early phase of laser-induced plasma after the femtosecond laser pulse. The temporal behavior of emission spectra of air plasma has been characterized. In comparison with the single-pulse scheme, the plasma emission obtained in the double-pulse scheme presents a more intense continuum along with several additional ionic lines. As only one line is available in the single-pulse scheme, the plasma temperature measurements were performed using only the relative line-to-continuum intensity ratio method, whereas the relative line-to-line intensity ratio method and the relative line-to-continuum intensity ratio method were used simultaneously to estimate the electron temperature in the double-pulse scheme. The results reveal that the temperature values obtained by the two methods in the double-pulse scheme agree. Moreover, this shows that the relative line-to-continuum intensity ratio method is suitable for early phase of laser-induced plasma diagnostics. The electron number density was estimated using the Stark broadening method. In the early phase of laser-induced plasma, the temporal evolution of the electron number density exhibits a power law decrease with delay time.