Wang Jiayi, Yu Haitao, Shen Jianqi, Yang Bin, Tropea Cameron
Opt Express. 2021 Jan 4;29(1):377-384. doi: 10.1364/OE.412937.
A vector ray-tracing model (VRT) has been developed to compute the optical caustics associated with the primary rainbow for an oblate spheroidal water drop illuminated by a Gaussian beam. By comparing the optical caustic structures (in terms of limiting rainbow and hyperbolic umbilic fringes) for a water drop with a Gaussian beam (GB) illumination with that for the same drop, but with parallel beam (PB) illumination, the influence of the Gaussian beam on the optical caustics is investigated. For a water drop with GB illumination and different drop/beam ratios (i.e., the ratio between the drop equatorial radius and the Gaussian beam waist), the location of cusp points and the curvature of the limiting rainbow fringe are also studied. We anticipate that these results not only confirm the approach to compute optical caustics for oblate spheroidal drops illuminated by a shaped beam, but may also lead to a new method for measuring the aspect ratio of spheroidal drops.
已开发出一种矢量光线追踪模型（VRT），用于计算由高斯光束照射的扁球形水滴与主虹相关的光焦散。通过比较高斯光束（GB）照明下的水滴与平行光束（PB）照明下的同一水滴的光焦散结构（根据极限虹和双曲脐条纹），研究了高斯光束对光焦散的影响。对于GB照明下的水滴以及不同的水滴/光束比（即水滴赤道半径与高斯光束腰斑半径之比），还研究了尖点位置和极限虹条纹的曲率。我们预计这些结果不仅能证实计算由成形光束照射的扁球形水滴光焦散的方法，还可能引出一种测量球形水滴纵横比的新方法。
