Nulling interferometry in the thermal IR is the most promising technique for direct detection of Earth-like exoplanets. This technique requires a π 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 π 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.
© 2003 Optical Society of America
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(310.0310) Thin films : Thin films
(310.1620) Thin films : Interference coatings
(350.1260) Other areas of optics : Astronomical optics
(350.1270) Other areas of optics : Astronomy and astrophysics
Frédéric Lemarquis and Pierre Riaud, "Thin-Film Achromatic Phase Shifters for Nulling Interferometry: Design Approach," Appl. Opt. 42, 6919-6928 (2003)