Light propagation through thin films, the amplitude and phase representation.

摘要

The amplitude and phase representation of classic electromagnetic waves is used to model light propagating through a stratified medium, with a continuous refractive index profile. This medium is assumed to be isotropic, non magnetic, electrically neutral, transparent, dielectric, with a linear response, but letting the electric permittivity vary along the z direction. No approximations regarding a slowly or strongly varying refractive index, compared to the wavelength, are made. This is particularly convenient when the refractive index varies on a wavelength scale. The case of a thin film at normal incidence is studied for various thicknesses and interface ranges. The corresponding nonlinear amplitude differential equation is numerically solved. The amplitude oscillations are construed in terms of counter-propagating waves and the film's reflectivity is evaluated.