Coupled-dipole approximation: predicting scattering by nonspherical marine organisms

Patricia G. Hull; Arlon J. Hunt; Mary S. Quinby-Hunt; Daniel B. Shapiro

doi:10.1117/12.49257

1 December 1991 Coupled-dipole approximation: predicting scattering by nonspherical marine organisms

Patricia G. Hull, Arlon J. Hunt, Mary S. Quinby-Hunt, Daniel B. Shapiro

Proceedings Volume 1537, Underwater Imaging, Photography, and Visibility; (1991) https://doi.org/10.1117/12.49257
Event: San Diego, '91, 1991, San Diego, CA, United States

Abstract

The polarization state of light in the ocean can be used to enhance visibility. The consequences of scattering from nonspherically-symmetric particles on light propagation and visibility in the ocean was investigated. To calculate scattering from nonspherical marine microorganisms, it is usually necessary to resort to approximate methods. One promising approximation is the coupled-dipole approach in which an arbitrarily-shaped object is divided into a number of identical elements arranged on a cubic lattice. Each element is treated as a spherical, dipolar oscillator with its polarizability specified by the real and imaginary parts of the index of refraction. Interactions between dipoles are included by determining the field at a particular dipole due to the incident field and the fields induced by the other dipole oscillators. The scattered field is then the sum of the fields due to each oscillator. The coupled-dipole method is promising because, in principle, an organism of any shape can be modeled, and all 16 elements of the scattering matrix calculated. This approach has been applied to calculate scattering from spherical particles to verify the limits of the approximation, and from other shapes to investigate the effects of nonsphericity and chirality on scattering. In particular, all 16 Mueller matrix elements for the scattering were calculated from a finite cylinder, a single- strand helix, 14-strand helix, and ensembles of these particles. The effects of pitch, size, wavelength, and complex index of refraction were investigated. The results provide insights into the magnitude and type of depolarization effects associated with various marine microorganisms containing these structures.

Citation Download Citation

Patricia G. Hull, Arlon J. Hunt, Mary S. Quinby-Hunt, and Daniel B. Shapiro "Coupled-dipole approximation: predicting scattering by nonspherical marine organisms", Proc. SPIE 1537, Underwater Imaging, Photography, and Visibility, (1 December 1991); https://doi.org/10.1117/12.49257

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