Interpretation of single-particle negative polarization at intermediate scattering angles

Area of Science:

• Electromagnetics
• Optical Physics
• Materials Science

Background:

• Understanding light scattering from particles is crucial in various scientific fields.
• The internal field of particles plays a key role in determining their far-field scattering properties.
• Irregular particle shapes present unique challenges in electromagnetic scattering analysis.

Purpose of the Study:

• To investigate the relationship between the internal electromagnetic field of irregular particles and their far-field scattering characteristics.
• To identify the specific components of the internal field that dominate scattering phenomena.
• To analyze the contribution of internal field modifications to polarization effects.

Main Methods:

• Utilized the discrete-dipole approximation (DDA) to model the internal electromagnetic field of particles.
• Systematically modified the internal field by selectively switching off the longitudinal component of dipoles based on energy density.
• Analyzed the resulting changes in far-field scattering patterns, focusing on linear polarization.

Main Results:

• A small fraction of dipoles (approximately 5%), termed 'core dipoles', located in the forward region of the particle, are responsible for negative linear polarization at intermediate scattering angles.
• The number of these core dipoles increases with particle asphericity.
• The interference patterns observed in scattered waves from these core dipoles are largely conserved for nonspherical particles, similar to spherical particles.

Conclusions:

• The longitudinal component of the internal field in specific 'core' dipoles is critical for negative linear polarization in irregular particles.
• Particle asphericity influences the extent of this effect by altering the number of contributing core dipoles.
• Wave interference principles remain robust across different particle geometries, offering insights into scattering mechanisms.