Optical fields and electromagnetic flux in thin films

Abstract The traditional method for characterizing optical thin films consists in calculating the proportion of light that is reflected and transmitted by the film. In this work, we present an alternative procedure based on the analysis of electromagnetic fields and energy flow within the film. Using our approach, we provide a unified description of a plethora of phenomena in three-layered structures, including frustrated total internal reflection, dielectric waveguiding, or surface plasmon resonance. Our approach highlights the distinguishing features of evanescent and damped waves in opposition to travelling waves, particularly those concerning the propagation of energy. The theoretical framework proposed here contributes to explicitly visualize the intrinsic difference between propagation in thin films and thicker media, providing physical insight into energy transport through them.