Anticaustics in a Fabry-Perot interferometer

Abstract

We address the response of a Fabry-Perot interferometer to a monochromatic point source. We calculate the anti -caustics (that is, the virtual wavefronts of null path difference) resulting from the successive internal reflections occurring in the system. They turn out to be a family of ellipsoids (or hyperboloids) of revolution, which allows us to reinterpret the operation of the Fabry-Perot interferometer from a geometrical point of view that facilitates comparison with other apparently disparate arrangements, such as Young's double slit.