Resonant-state expansion for open optical systems: Generalization to magnetic, chiral, and bi-anisotropic materials

TL;DR

This paper extends the resonant-state expansion method to include magnetic, chiral, and bi-anisotropic materials in open optical systems, broadening its applicability in electrodynamics.

Contribution

The generalization of the resonant-state expansion method to handle magnetic, chiral, and bi-anisotropic materials, with a new normalization approach for resonant states.

Findings

Matrix eigenvalue equation remains unchanged

Perturbation matrix elements now include permittivity, permeability, and bi-anisotropy tensors

Normalization of resonant states in electric and magnetic fields is established

Abstract

The resonant-state expansion, a recently developed powerful method in electrodynamics, is generalized here for open optical systems containing magnetic, chiral, or bi-anisotropic materials. It is shown that the key matrix eigenvalue equation of the method remains the same, but the matrix elements of the perturbation now contain variations of the permittivity, permeability, and bi-anisotropy tensors. A general normalization of resonant states in terms of the electric and magnetic fields is presented.