Resonant state expansion for Transverse Electric modes of two-dimensional open optical systems

Abstract

The resonant state expansion (RSE), a rigorous perturbative method in electrodynamics, is formulated for Transverse Electrodynamic modes of an effectively $2$-dimensional system. The RSE is a perturbation theory based on the Lippmann Schwinger Green's function equation and requires knowledge of the Green's function of the unperturbed system constructed from Resonant-states. I use the analytic Green's function for the magnetic field to normalize the modes appearing in the corresponding spectral Green's function. This use of the residue and cut of the analytic Green's function is a solution to the failure of the flux volume integral method of normalization for continuum states, a problem which is discussed in detail in this manuscript. In brief, the flux volume integral fails for continuum states because they are not true resonance. An analytic relation between normalized magnetic and electric modes is developed as part of the solution to these difficulties.The complex eigenfrequencies of modes are calculated using the RSE for the case of a homogeneous perturbation.