On the concept of absorption for a Fabry–Perot interferometer

Abstract

We argue that the Fabry–Perot interferometer should be modeled as a transparent medium between two absorbing coatings of finite thickness. Using the scattering-matrix formalism, we show that the transmittance obeys an Airy function, but not the reflectance, because of absorption and the coupling between the multiply reflected waves in the coatings. The model allows us to compute the absorptance in each coating and to explain a number of previous experimental results. The Stokes relations are generalized for this model.