超快激光成丝诱导空气激光的机制研究

Recently, lasing in air induced by ultrafast laser filamentation has attracted much more interest due to its potential application in atmosphere remote sensing. Air laser can remotely generate ultraviolet source which will overcome the disadvantage of short distance by fluorescence spectrum sensing technology. The research of lasing in air induced by ultrafast laser filamentation is a brand new subject in recent years. The results are relatively limited. In this project we will study the mechanism of lasing in air induced by ultrafast laser filamentation. The content of research includes: identification of the main physical mechanism of air laser is amplified spontaneous emission or four-wave mixing nonlinear effort; experimental characterization of various parameters impact on the property of air laser, such as wavelength, pulse width and gain etc;investigation the effort of the multiple filaments on the air laser. The purpose of our program is getting highly intense, well coherent and directional ultraviolet lasing in air, establishing the physical model in order to provide theoretical basis in the application of atmosphere remote sensing.It is expected that we can promote the interrelated fields to the international advanced level, through this investigation in the project.

近年来，超快激光成丝诱导空气激光的现象在遥感大气测量中具有潜在的应用前景，吸引了国内外众多学者的兴趣。空气激光可以远程产生紫外光源，解决紫外荧光光谱测量技术中传输距离短的问题。基于超快激光成丝现象诱导空气激光的研究是近几年才发展起来的新兴课题，目前尚在研究初期，国内外研究成果也较为有限。本项目拟开展超快激光成丝诱导紫外激光辐射的机制研究。研究内容包括：明确空气激光的主要物理机制是放大自发辐射还是四波混频非线性效应引起的；实验表征各种激励源、环境参数对空气激光辐射波长，脉冲宽度、增益等特性的影响；研究多丝对空气激光品质参数的影响机制。项目预期目标是得到强度高，相干度和方向性好，高光学增益的诱导紫外激光脉冲，建立物理模型，为实现其在遥感探测领域的实际应用提供理论基础。我们希望通过该项目研究工作，为推动国内相关研究领域向国际领先水平发展做出贡献。

超快激光成丝现象一直是非线性光学领域的前沿课题，本项目拟开展超快激光成丝诱导空气激光辐射现象物理机制的研究，在非线性光谱学和远程遥感领域有着非常重要的应用前景。. 本项目首先研究了超快激光脉冲的非线性传输特性。研究了超快激光经过透镜、轴锥镜和光学相位板等微纳光学器件之后成丝的空间和时间分布情况。结果表明利用微纳光学器件可以延长光丝的长度，达到了控制多丝的目标，有助于实现对大气污染物的远程探测。与此同时，我们还发现了脉冲压缩现象，可用于产生阿秒脉冲和高次谐波。. 接着，我们研究了超快激光成丝诱导空气激光辐射的物理机制，对空气激光辐射过程中氮气分子振动、转动能级粒子数的演化进行了深入的研究，建立物理模型。借助用相位板等微纳光学器件，研究了多丝对空气激光辐射特性的影响，我们发现氮分子和氮离子的背向和侧向荧光光谱信号的强度均随成丝的数量增强，自发辐射放大系数也有着明显的增大。. 最后我们研究了超快激光成丝诱导空气激光物理现象对于光谱成分的测量。超快激光成丝诱导击穿光谱技术可以有效的分析样品元素成分，在快速原位测量、在线分析、多元素实时分析等方面具有较大优势，可以应用于固体、液体、气体样品的探测。借助其在超快激光成丝探测非线性光谱方面表现的优势，我们探测和分析了铜、铝锌合金、氯化钠气溶胶和无水乙醇气溶胶的指纹荧光谱，为大气污染物的探测提供了新的更有效的途径。