Hodges J T, Gréhan G, Gouesbet G, Presser C
Appl Opt. 1995 Apr 20;34(12):2120-32. doi: 10.1364/AO.34.002120.
The forward scattering of a Gaussian laser beam by a spherical particle located along the beam axis is analyzed with the generalized Lorenz-Mie theory (GLMT) and with diffraction theory. Forwardscattering and near-forward-scattering profiles from electrodynamically levitated droplets, 51.6 µm in diameter, are also presented and compared with GLMT-based predictions. The total intensity in the forward direction, formed by the superposition of the incident and the scattered fields, is found to correlate with the particle-extinction cross section, the particle diameter, and the beam width. Based on comparison with the GLMT, the diffraction solution is accurate when beam widths that are approximately greater than or equal to the particle diameter are considered and when large particles that have an extinction efficiency near the asymptotic value of 2 are considered. However, diffraction fails to describe the forward intensity for more tightly focused beams. The experimental observations, which are in good agreement with GLMT-based predictions, reveal that the total intensity profile about the forward direction is quite sensitive to particle axial position within a Gaussian beam. These finite beam effects are significant when the ratio of the beam to the particle diameter is less than approximately 5:1. For larger beam-to-particle-diameter ratios, the total field in the forward direction is dominated by the incident beam.
利用广义洛伦兹 - 米氏理论（GLMT）和衍射理论分析了沿光束轴放置的球形粒子对高斯激光束的前向散射。还给出了直径为51.6 µm的电动悬浮液滴的前向散射和近前向散射分布，并与基于GLMT的预测结果进行了比较。由入射场和散射场叠加形成的前向总强度与粒子消光截面、粒子直径和光束宽度相关。与GLMT相比，当考虑光束宽度大约大于或等于粒子直径，以及考虑消光效率接近渐近值2的大粒子时，衍射解是准确的。然而，衍射无法描述聚焦更紧密光束的前向强度。与基于GLMT的预测结果吻合良好的实验观察结果表明，关于前向方向的总强度分布对高斯光束内粒子的轴向位置非常敏感。当光束与粒子直径之比小于约5:1时，这些有限光束效应很显著。对于较大的光束与粒子直径之比，前向总场由入射光束主导。
