Kevin Vynck
LP2N, CNRS – Institut d’Optique Graduate School – Univ. Bordeaux, France.
Recent developments in the electromagnetic modelling of complex nanostructures
Disordered assemblies of resonant nano-objects incorporated in planar geometries are becoming widespread in photonics. A broad variety of electromagnetic particles made of dielectric or metallic materials and having complex (non-spherical) shapes can nowadays be synthesized by colloidal means [1] and self-assembled onto arbitrary substrates. The rich optical properties of such complex nanostructured surfaces stem from the optical resonances of the individual particles, the interaction of the particles with a stratified medium and the mutual interaction between neighboring particles. Their modelling has however remained elusive up to now due to the difficulty to consider simultaneously the coherent phenomena occurring at the level of the individual particle (nano-scale) and at the level of the particle ensemble (meso-scale).
In this seminar, I will introduce a novel numerical method, named “Global Polarizability Matrix” (GPM), that enables a very efficient modelling of large ensembles of complex particles incorporated in stratified media [2]. The GPM method requires a remarkably low memory usage compared to Maxwell’s equations solvers like finite elements or finite differences methods. It can also handle situations in which the scattering elements are touching or even crossing planar interfaces, unlike the popular T-matrix method [3], thereby opening new perspectives in the study of complex optical nanostructures. I will conclude by presenting an analytical, multiple-scattering model for the reflectance properties of monolayers of resonant particles on layered substrates [4]. The model provides considerable insight onto the role of particle resonances and correlated disorder on specular and diffuse scattering. A very good agreement is found when comparing the model predictions with those obtained numerically with the GPM method.
References
[1] M. Treguer-Delapierre et al., Gold Bull. 41, 195 (2008); M. L. De Marco et al., Angew. Chem. Int. Ed. 57, 4478 (2018).
[2] M. Bertrand, A. Devilez, J.-P. Hugonin, P. Lalanne, and K. Vynck, J. Opt. Soc. Am. A 37, 70-83 (2020); M. Bertrand, J.-P. Hugonin, P. Lalanne, and K. Vynck, in preparation.
[3] M. I. Mishchenko, J. W. Hovenier, and L. D. Travis, “Light scattering by nonspherical particles: theory, measurements, and applications” (IOP, 2000)
[4] K. Vynck, R. Pacanowski, A. Dufay, X. Granier, and P. Lalanne, submitted.