Local field intensity in aggregates illuminated by diffuse light: T matrix approach

Abstract

We derive an analytic expression for the local field intensity in an aggregate of particles illuminated by diffuse light (T matrix formalism). To be precise, the diffuse light average is obtained by averaging the electromagnetic response from plane waves over all possible incident field direction polarizations. We applied this new averaging formula to analyze variations in the electromagnetic couplings between two isotropic spheres as a function of their separation distance. The numerical calculations were performed with the recursive centered T matrix algorithm (RCTMA), one of the known analytical solutions of the multiple scattering equation of light. Illustrative calculations clearly demonstrate that diffuse averaging has a large smoothing effect on the strong angular and local variations in the field intensities that are omnipresent in orientation fixed calculations. We believe that this formalism can be a valuable tool in the analysis of electromagnetic couplings in dense random heterogeneous media, in which light propagation is dominated by a scalar diffusion behavior.

Orientation Averaging of Optical Chirality Near Nanoparticles and Aggregates

“…This is a particular strength of the method which has led to analytical formulas for orientation-averaged quantities such as far-field cross-sections [41,45]. Such results were recently extended by Rockstuhl and coworkers for optical activity [26], and by Stout and co-workers for near-field quantities in clusters of spherical particles [46,47]. We extend here these previous results to the calculation of orientationaveraged near-field optical chirality.…”

Orientation-averaged light scattering by nanoparticle clusters: far-field and near-field benchmarks of numerical cubature methods

“…The computational method itself is also subject to other sources of error, such as the fineness of a mesh when the scatterers are discretised in FEM, FDTD or DDA; in the T -matrix method employed here, the key convergence parameter is the maximum multipolar order l max which is used to truncate field expansions 53 . In our implementation, note that l max refers to scatterer-centred expansions 13,22 . Remarkably, we find no interaction between N inc and l max when studying the convergence of orientation-averaged quantities.…”

“…incident and scattered fields yield analytical formulas for orientation-averaged optical properties. This powerful formalism enables benchmark calculations for various quantities of interest, which include orientation-averaged extinction, scattering and absorption 19,20 , circular dichroism 21 , but also near-field intensity 22 and local degree of optical chirality 23,24 . Although analytical, these orientationaveraged expressions can become quite involved in the case of near-field quantities, requiring the costly evaluation of translation matrices for each evaluation point.…”

Comprehensive T-matrix reference database: A 2012–2013 update

“…2.23. T-matrix calculations of internal, surface, and local fields [13,23,26,31,37,40,112,134,153,162,198,206,207,247].…”

“…T-matrix calculations for finite circular cylinders[21,36,51,57,61,67,78,80,103,128,129,145,147,149,158,180,211,219,222,226,227,235,237,240,241,252]. ,[13][14][15]25,[28][29][30][31]37,40,41,44,45,[48][49][50]54,72,74,82, 92,93,102,110,112,119,120,122,123,125,134,137,141-143,…”