Modification of laser-induced fluorescence spectrum by additional azimuthal Doppler effect in optical vortex beams
Modification of laser-induced fluorescence spectrum by additional azimuthal Doppler effect in optical vortex beams
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DOI：
10.35848/1347-4065/ab72cb
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发表时间：
2020-03
影响因子：
1.5
通讯作者：
S. Yoshimura;K. Terasaka;M. Aramaki
中科院分区：
文献类型：
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作者：
S. Yoshimura;K. Terasaka;M. Aramaki
激光诱导荧光 (LIF) 方法是测量等离子体中原子和离子物质流速的强大工具。携带光轨道角动量的光学涡旋光束有可能扩展 LIF 方法的流速测量能力，因为在光学涡旋光束中移动的原子在方位角方向上会经历额外的多普勒效应。对用光学涡旋光束代替常用的平面波状光束获得的 LIF 光谱进行了数值评估。事实证明，光谱的修改可以用来检测垂直于激光路径的快速流动，这在原理上是不可能通过传统方法观察到的。还讨论了使用频谱的标准偏差作为垂直流速的指标。
Laser-induced fluorescence (LIF) method is a powerful tool to measure flow velocities of atomic and ionic species in a plasma. Optical vortex beams, which carry orbital angular momentum of light, have a potential to expand the capability of flow velocity measurements with LIF method, because an atom moving in an optical vortex beam experiences additional Doppler effect in the azimuthal direction. The LIF spectra obtained by substituting a commonly-used plane-wave-like beam with an optical vortex beam have been numerically evaluated. It is demonstrated that modification of the spectrum can be used to detect a fast flow perpendicular to the laser path, which is impossible to be observed by conventional method in principle. The use of standard deviation of the spectrum as an index of perpendicular flow velocity is also discussed.