由自导成丝效应产生的超连续辐射具有超宽带光谱、后向散射增强等一系列新特征,为激光雷达大气探测开辟了新的领域。通过测量飞秒激光脉冲自导光丝超连续辐射散射的角度分布,对不同条件空气中自导光丝产生的超连续辐射后向散射特性进行了实验研究。结果表明,在洁净空气和含气溶胶的空气中,自导光丝的超连续辐射都呈现出明显的后向散射增强特性。同时对超连续辐射后向散射的测量值进行拟合,拟合结果表明超连续辐射后向散射角分布满足洛伦兹(Lorentz)函数,在洁净空气中其角宽度为6.4°,后向180°时归一化散射强度是瑞利散射的3.2倍。超连续辐射沿光丝前向呈锥形辐射,其前向散射具有明显的波长依赖关系; 而后向散射无明显的波长依赖关系。

New characteristics of supercontinuum emission generating along with ultrashort femtosecond laser self-guided propagating in air, such as ultra wide band spectrum and backscattering enhancement, produce a new study field for the development of atmosphere detection lidar. The backscattering properties of supercontinuum emission from a self-guided filament generated by femtosecond laser are researched by measuring the angular distribution of supercontinuum emission at different conditions of air. The results show the backscattering of supercontinuum emission from a filament is enhanced in clear air and dusty air with aerosol. And by fitting the experimental data of the backscattering of supercontinuum emission, it is found that the angular distribution of supercontinuum backscattering satisfy Lorentz function; in clear air the angle width is 6.4°, the normalized backscattering intensity increases 3.2 times as compared with Rayleigh scattering at 180°. Along the filament, the frontward supercontinuum emission exhibits the conical emission, so frontward scattering is obviously dependent on wavelengths; the backward scattering shows no obvious dependence on wavelengths.