Fast Simulation of Light Scattering and Harmonic Generation in Axially Symmetric Structures in COMSOL

Abstract

The study of electromagnetic scattering in optics and nanophotonics is crucial for understanding complex nanostructures and optical devices. However, numerical analysis of scattering spectra, even for simple shape nanocavities, presents significant computational challenges. This paper focuses on simplifying the simulation process by utilizing system symmetries and the separation of variables, which reduces the dimension of the problem. Specifically, we present a practical guide to efficiently simulate linear and nonlinear scattering problems in COMSOL Multiphysics for axisymmetric objects. This includes computing the scattering cross-section, multipolar decomposition, optical forces, and second harmonic generation (SHG). We show that by reducing the calculation time we are able to analyze the generation spectra of SH under varying geometrical parameters of nanoantennas across a broad range. Additionally, we study the increase in SHG within a high-Q state at the band edge in a chain of dielectric discs with lengths ranging from 5 to 20 particles. We also accompany the provided guide with the ready-to-run COMSOL models.

Nonlinear circular dichroism in achiral dielectric nanoparticles

“…One of the main things to do here is rewriting χ(q) tensor in spherical coordinates, as it was done, e.g. in [49,50] for χ (2) . After that, we get all possible additional momentum projections m χ (it is the multiplier which stands in the terms like sin(m χ φ) or cos(m χ φ) if one looks at the tensor components written in cylindrical coordinates), as well as differences ∆m χ = m χ − m ′ χ between all possible different values.…”