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The cda package implements the coupled-dipole approximation for electromagnetic scattering by sparse collections of subwavelength particles, with a particular focus on plasmonic nanoparticles in the visible regime. The interaction matrix, and the solution of the linear system of coupled-dipole equations are executed in C++ code for speed; convenient wrapper functions are provided at the R level to generate the particle clusters, calculate the extinction, scattering, and absorption of light by particles with linearly and circularly polarised light. Functions are also provided to calculate orientation-averaged circular dichroism, and display clusters of nanoparticles in three dimensions using OpenGL or povray.

This wiki provides information to start using the package.

to get started

various utility functions

Basic example

Simulating extinction and optical activity from a dimer of gold nanorods

Demos and tutorials

clusters generate 3D views of some predefined cluster shapes using RGL rendering or povray

dimer_linear extinction spectrum of a dimer of gold nanorods

dimer_cd circular dichroism for a chiral dimer of gold nanorods

helix_cd circular dichroism for a helix of gold nanoparticles

diffractive_chain extinction spectrum of a square array of gold nanorods

lattice_sum lattice sum for a 2D square array of dipoles

multiple_incidence dispersion plot with varying angles of incidence

Technical aspects and tests

timing_inversion is it faster to invert the interaction matrix once, or solve a linear system for multiple angles of incidence?

averaging_method compares the performance of GL quadrature, QMC, and basic grid

trivial_tests checks the correctness of the results in trivial situations (non-chiral cluster, translations, rotations, inversion).