Kuga Y, Ishimaru A
Appl Opt. 1989 Jun 1;28(11):2165-9. doi: 10.1364/AO.28.002165.
Recently, the backscattering enhancement by densely distributed particles of a size comparable to the wavelength was reported. It has been explained as the constructive interference of two waves traveling in opposite directions. This enhancement was observed only in densely distributed particles, and its existence in sparsely distributed media has not been verified yet. In this paper we present the experimental evidence of backscattering enhancement by sparsely distributed very large particles. Experiments are conducted using 45-microm latex particles which are approximately 100 times the wavelength. Both copolarized and crosspolarized components are measured for different particle concentrations. Unlike for small particles, backscattering enhancement is most noticeable when the particle concentration is low. The angular width of the peak is comparable to the ratio (wavelength)/(particle size) and is independent of the optical distance.
最近，有报道称尺寸与波长相当的密集分布粒子会增强后向散射。这被解释为沿相反方向传播的两列波的相长干涉。这种增强仅在密集分布的粒子中观察到，其在稀疏分布介质中的存在尚未得到证实。在本文中，我们给出了稀疏分布的非常大的粒子增强后向散射的实验证据。实验使用的是45微米的乳胶粒子，其大小约为波长的100倍。针对不同的粒子浓度测量了共极化和交叉极化分量。与小粒子不同，当粒子浓度较低时，后向散射增强最为明显。峰值的角宽度与（波长）/（粒子大小）的比值相当，并且与光学距离无关。
