We investigate the T-matrix approach for the simulation of light scattering by an oblate particle near a planar interface. Its validity has been in question if the interface intersects the particle's circumscribing sphere, where the spherical wave expansion of the scattered field can diverge. However, the plane wave expansion of the scattered field converges everywhere below the particle, and in particular at the planar interface. We demonstrate that the particle-interface scattering interaction is correctly accounted for through a plane wave expansion in combination with Fresnel reflection at the planar interface. We present an in-depth analysis of the involved convergence mechanisms, which are governed by the transformation properties between spherical and plane waves. The method is illustrated with the cases of spherical and oblate spheroidal nanoparticles near a perfectly conducting interface, and its accuracy is demonstrated for different scatterer arrangements and materials.
The simulation of light scattering by particles on a substrate with the Tmatrix method relies on the expansion of the scattered field in spherical waves, followed by a plane wave expansion to allow the evaluation of the reflection from the substrate. In practice, the plane wave expansion (i.e., the Sommerfeld integrals) needs to be truncated at a maximal in-plane wavenumber κ max . An appropriate selection of κ max is essential: counter-intuitively, the overall accuracy can degrade significantly if the integrals are truncated with a too large value. In this paper, we propose an empirical formula for the selection of κ max and discuss its application using a number of example simulations with dielectric and metallic oblate spheroids on dielectric and metallic substrates. The computed differential scattering cross sections are compared to results obtained from the discrete-sources method.
The computation of light scattering by the superposition T-matrix scheme has been so far restricted to systems made of particles that are either sparsely distributed or of near-spherical shape. In this work, we extend the range of applicability of the T-matrix method by accounting for the coupling of scattered fields between highly non-spherical particles in close vicinity. This is achieved using an alternative formulation of the translation operator for spherical vector wave functions, based on a plane wave expansion of the particle's scattered electromagnetic field. The accuracy and versatility of the present approach is demonstrated by simulating arbitrarily oriented and densely packed spheroids, for both, dielectric and metallic particles.
In this work, the extraction of waveguided and substrate modes in organic light emitting diodes (OLEDs) is improved by using compact light scattering layers composed of a disordered 2D array of TiO2 nanopillars. The TiO2 nanopillars are fabricated by combining a self‐assembly and a solvent‐assisted lift‐off process, and are further planarized by a 250 nm thin epoxy‐based photoresist layer to facilitate their anode deposition and integration within the OLED stack. This fabrication route allows engineering internal light outcoupling elements with a limited amount of parasitic absorption and with easily tunable light scattering properties that are effective over a broad spectral and angular range. Taking the example of a monochromatic bottom emitting OLED (λpeak = 520 nm), the authors demonstrate an efficiency enhancement of +22%rel upon the incorporation of the planarized light extraction layer as well as ameliorated angular emission characteristics. This approach can be integrated in a high‐throughput fabrication routine and straightforwardly extended to other OLED layouts.
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