Coupled Dipole Approximation for Modeling Large Scale Random Media

2008 ◽  
Author(s):  
Sergey Sukhov ◽  
David Haefner ◽  
Aristide Dogariu
Keyword(s):  
Random Media ◽  
Large Scale ◽  
Dipole Approximation ◽  
Coupled Dipole Approximation

scholarly journals Coupled dipole approximation across the Γ-point in a finite-sized nanoparticle array

2017 ◽  
Vol 375 (2090) ◽  
pp. 20160316 ◽  
Author(s):  
J.-P. Martikainen ◽  
A. J. Moilanen ◽  
P. Törmä
Keyword(s):  
Real Space ◽  
Dipole Approximation ◽  
Incident Field ◽  
Nanoparticle Array ◽  
Radiation Patterns ◽  
New Horizons ◽  
Coupled Dipole Approximation

We study the response of a finite-sized nanoparticle array to an incident field in the vicinity of the Γ-point of the lattice. Using the coupled dipole approximation, we find that the dipole distributions can be strongly inhomogeneous and that strong modulations appear as the energy is above the Γ-point. We highlight how this is reflected in real-space extinction efficiencies as well as in radiation patterns from the finite-sized array. This article is part of the themed issue ‘New horizons for nanophotonics’.

Coupled-dipole approximation: predicting scattering by nonspherical marine organisms

1991 ◽  
Author(s):  
Patricia G. Hull ◽  
Arlon J. Hunt ◽  
Mary S. Quinby-Hunt ◽  
Daniel B. Shapiro
Keyword(s):  
Dipole Approximation ◽  
Marine Organisms ◽  
Coupled Dipole Approximation

2-D random media with ellipsoidal autocorrelation functions

Geophysics ◽  
1993 ◽  
Vol 58 (9) ◽  
pp. 1359-1372 ◽  
Author(s):  
L. T. Ikelle ◽  
S. K. Yung ◽  
F. Daube
Keyword(s):  
Aspect Ratio ◽  
Seismic Data ◽  
Random Media ◽  
Large Scale ◽  
Seismic Waves ◽  
Homogeneous Medium ◽  
Small Scale ◽  
Arrival Times ◽  
The Earth ◽  
Pulse Arrival

The integration of surface seismic data with borehole seismic data and well‐log data requires a model of the earth which can explain all these measurements. We have chosen a model that consists of large and small scale inhomogeneities: the large scale inhomogeneities are the mean characteristics of the earth while the small scale inhomogeneities are fluctuations from these mean values. In this paper, we consider a two‐dimensional (2-D) model where the large scale inhomogeneities are represented by a homogeneous medium and small scale inhomogeneities are randomly distributed inside the homogeneous medium. The random distribution is characterized by an ellipsoidal autocorrelation function in the medium properties. The ellipsoidal autocorrelation function allows the parameterization of small scale inhomogeneities by two independent autocorrelation lengths a and b in the horizontal and the vertical Cartesian directions, respectively. Thus we can describe media in which the inhomogeneities are isotropic (a = b), or elongated in a direction parallel to either of the two Cartesian directions (a > b, a < b), or even taken to infinite extent in either dimension (e.g., a = infinity, b = finite: a 1-D medium) by the appropriate choice of the autocorrelation lengths. We also examine the response of seismic waves to this form of inhomogeneity. To do this in an accurate way, we used the finite‐difference technique to simulate seismic waves. Special care is taken to minimize errors due to grid dispersion and grid anisotropy. The source‐receiver configuration consists of receivers distributed along a quarter of a circle centered at the source point, so that the angle between the source‐receiver direction and the vertical Cartesian direction varies from 0 to 90 degrees. Pulse broadening, coda, and anisotropy (transverse isotropy) due to small scale inhomogeneities are clearly apparent in the synthetic seismograms. These properties can be recast as functions of the aspect ratio [Formula: see text] of the medium, especially the anisotropy and coda. For media with zero aspect ratio (1-D media), the coda energy is dominant at large angles. The coda energy gradually becomes uniformly distributed with respect to angle as the aspect ratio increases to unity. Our numerical results also suggest that, for small values of aspect ratio, the anisotropic behavior (i.e., the variations of pulse arrival times with angle) of the 2-D random media is similar to that of a 1-D random medium. The arrival times agree with the effective medium theory. As the aspect ratio increases to unity, the variations of pulse arrival times with angle gradually become isotropic. To retain the anisotropic behavior beyond the geometrical critical angle, we have used a low‐frequency pulse with a nonzero dc component.

Large Scale Simulations of Elastic Light Scattering by a Fast Discrete Dipole Approximation

1998 ◽  
Vol 09 (01) ◽  
pp. 87-102 ◽  
Author(s):  
A. G. Hoekstra ◽  
M. D. Grimminck ◽  
P. M. A. Sloot
Keyword(s):  
Light Scattering ◽  
Blood Cells ◽  
Large Scale ◽  
Incident Light ◽  
Spherical Inclusion ◽  
White Blood Cells ◽  
Dipole Approximation ◽  
Discrete Dipole Approximation ◽  
Dust Particles ◽  
Elastic Light Scattering

Simulation of Elastic Light Scattering from arbitrary shaped particles in the resonance region (i.e., with a dimension of several wavelengths of the incident light) is a long standing challenge. By employing the combination of a simulation kernel with low computational complexity, implemented on powerful High Performance Computing systems, we are now able to push the limits of simulation of scattering of visible light towards particles with dimensions up to 10 micrometers. This allows for the first time the simulation of realistic and highly relevant light scattering experiments, such as scattering from human red — or white blood cells, or scattering from large soot — or dust particles. We use the Discrete Dipole Approximation to simulate the light scattering process. In this paper we report on a parallel Fast Discrete Dipole Approximation, and we will show the performance of the resulting code, running under PVM on a 32-node Parsytec CC. Furthermore, as an example we present results of a simulation of scattering from human white blood cells. In a first approximation the Lymphocyte is modeled as a sphere with a spherical inclusion. We investigate the influence of the position of the inner sphere, modeling the nucleus of a Lymphocyte, on the light scattering signals.

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