ON THE CONCEPT OF ABSORPTION FOR A FABRY-PEROT-INTERFEROMETER

We argue that the Fabry-Perot interferometer should be modeled as a tr ansparent medium between two absorbing coatings of finite thickness. U sing the scattering-matrix formalism, we show that the transmittance o beys 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 relatio ns are generalized for this model. (C) 1996 American Association of Ph ysics Teachers.