Light scattering in stratified backgrounds: a surface integral equation approach

Modeling nanophotonic systems with complex or layered substrates is difficult due to effects like waveguide modes, surface plasmon polaritons or Bloch surface waves supported by the stratified background. Traditional differential methods, such as finite differences or finite elements, demand large domains and struggle with absorbing boundary conditions and perfectly matched layers since energy must be allowed to escape the computation window not only in the form of free-space scattered light, but also of guided modes. The surface integral equation method overcomes these challenges by incorporating the stratified background into the Green’s tensor, requiring discretization only of the scatterers’ surfaces and fulfilling the boundary condition perfectly, irrespective of the background complexity. This greatly reduces computational effort, though it results in dense matrices and complex Green’s tensor evaluations. This presentation will include some of the technical details associated with the method and present some experimentally-relevant situations of scatterers above or within stratified backgrounds.