Interrelating angular scattering characteristics to internal electric fields for wavelength-scale spherical particles

The origin of negative polarization observed in the backscattering region of wavelength-scale spherical particles has been attributed to surface waves. We demonstrate that the internal-field components have a more prominent role in producing this phenomenon. The internal field of spherical particles is computed for different size parameters and refractive indices. The effect of the internal field on the scattered field is studied by modifying the field components of the discretized internal field of the particle. The incident field is assumed to be X-polarized and to propagate in the direction of the Z-axis. For the different internal-field cases, we tabulate the asymmetry parameters of the phase functions, and the so-called polarization norms and asymmetry parameters. We show that both the Z- and X-component of the internal field cause negative polarization, the Z-component directly and the X-component through constructive interference between the contributions from different parts of the particle interior. The former component has a more pronounced influence on the overall polarization, which is readily seen in the polarization norm and asymmetry parameter becoming predominantly more positive for all parameters investigated. The latter component dominates the negative linear polarization close to the backscattering direction and is additionally seen to be responsible for the backscattering peak.