Numerical Simulation of Laser Light Scattering by a Single Particle Based on Direct Solution of Discretized Maxwell's Equation

摘要

Prediction of light scattering is required to develop the optical measuring techniques for detect- ing the size and shape of an individual non-spherical particle. However, the applicability of well known Lorentz-Mie theory is fairly limited and is unsuitable for this purpose. In this paper, we examine the feasibility of a direct solution method of Maxwell's electromagnetic wave equation for predicting the laser light scattering by a non-spherical object. It is confirmed that the Cartesian coordinate system is available for predicting light scattering, even if the shape of a scattering object is stepwise approximated based on the Cartesian coordinate system. That is, a complex coordinate system matched to the shape of a scattering object is not required. In addition, it is clarified that the electromagnetic field produced in the near field of a scattering object remarkably varies depending on its cross-sectional shape even if the scattering patterns are almost same in the backward far field. This suggests that the estimation of multiple scattering effects in the optical particle sizing tech- niques should be conducted based on the near field scattering pattern. The method employed in this paper is suitable also for these purposes because this method can easily deal with a closely allocated group of scattering objects.