紧聚焦条件下飞秒激光产生空气等离子体的动态演化特性

发布时间：2018-03-19 06:29

本文选题：激光光学　切入点：飞秒激光传输　出处：《中国激光》2017年07期 　论文类型：期刊论文

【摘要】：采用具有旋转对称性的三维空间电离模型,对紧聚焦条件下中心波长为800nm、脉冲宽度为50fs的激光脉冲产生的空气等离子体的时间和空间特性进行了数值模拟,揭示了整个等离子体区折射率的动态演化过程。计算结果表明:当激光脉冲开始聚焦时,靠近焦点前方的空气首先被电离,随后产生一个中心区域达到饱和、边缘具有很高折射率梯度的水滴状等离子区域;随着激光脉冲继续向焦点传播并越过焦点,等离子体区进一步向前延伸,直至在焦点前后形成一个近乎对称的双卵形结构;脉冲通过焦点区域后,空气等离子体强度沿传播方向逐渐减弱,直到最终完全消失;在10倍物镜聚焦下,脉冲能量为500μJ、脉冲宽度为50fs的激光脉冲产生的空气等离子体由产生到消失的整个过程约持续3ps。理论计算结果与30kPa低气压环境下的实验观测结果相吻合。
[Abstract]:Using a three-dimensional spatial ionization model with rotational symmetry, the temporal and spatial characteristics of air plasma produced by a laser pulse with a central wavelength of 800 nm and a pulse width of 50 fs are numerically simulated under the condition of compact focusing. The dynamic evolution of refractive index in the whole plasma region is revealed. The calculated results show that when the laser pulse begins to focus, the air near the focal point is first ionized and then a central region is saturated. As the laser pulse continues to propagate to the focal point and crosses the focus, the plasma region further extends forward until a nearly symmetrical double oval structure is formed before and after the focal point. After the pulse passes through the focal area, the intensity of the air plasma decreases gradually along the direction of propagation, and finally disappears completely. The pulse energy is 500 渭 J and the pulse width is 50 fs. The whole process from generation to disappearance of the air plasma lasts about 3 ps.The theoretical calculation results are in agreement with the experimental results at 30 KPA low pressure.
【作者单位】：南开大学现代光学研究所光学信息技术科学教育部重点实验室;
【基金】：国家自然科学基金(11274185,61137001)
【分类号】：O437;O53

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