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Multiphysics Simulation: An IEEE Spectrum Insert
Manager’s Guide

Scattering of Electromagnetic Waves by Particles

S. Yushanov, J. Crompton, and K. C. Koppenhoefer, Altasim Technologies, OH, USA

When electromagnetic waves propagate through matter, they interact with inhomogeneities and particles that can locally disrupt the electron distribution, causing electromagnetic radiation and scattering. One mathematical model used to describe the scattering of electromagnetic waves is called Mie scattering, which provides a general solution independent of particle size. Examples of phenomena where Mie scattering applies include dust in the air, oil in water, and measuring cell nuclei in biological systems.

In order to model Mie scattering, Maxwell's equations are used to represent the scattered, incident, and internal fields, which are represented by infinite series when solved with an analytical approach. Using COMSOL Multiphysics, AltaSim Technologies has developed a simulation to easily obtain the rates of absorption, scattering, and extinction of electromagnetic energy, and the radiation forces present. They have used a perfectly matched layer (PML), far-field calculations, and surface boundary conditions to calculate the scattered energy. Their computational model contributes to the visualization and understanding of the interactions between particles and incident electromagnetic waves.

Distribution of the z-component of the electric field due to scattering of the incident electromagnetic wave by a particle of 0.1μm radius. The arrows show the time-averaged power flow of the relative fields at a frequency of 950 THz.