title: Thin-film achromatic phase shifters for nulling interferometry: design approach.
abstract: Nulling interferometry in the thermal IR is the most promising technique for direct detection of Earth-like exoplanets. This technique requires a pi phase shifter for the parent star of the planet to be completely extinguished by destructive interference. We investigate how thin films can be used to design pi achromatic phase shifters. The design approach that we propose works on reflection and can be carried out by two steps, namely, the design of a mirror and an antireflection structure with no constraint on the phase properties of the thin film stacks. Phase-shift accuracy is derived analytically, and a numerical example illustrates this concept.
authors.affiliation: Institut Fresnel, Unité Mixte de Recherche, 6133 du Centre National de la Recherche Scientifique, Ecole Nationale Supérieure de Physique de Marseille, Domaine Universitaire de Saint Jérome, 13397 Marseille Cedex 20, France. frederic.lemarquis@fresnel.fr
authors.forename: Frédéric
authors.initials: F
authors.lastname: Lemarquis
authors.forename: Pierre
authors.initials: P
authors.lastname: Riaud