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Proceedings Paper

Approaches for achieving broadband achromatic phase shifts for visible nulling coronagraphy
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Paper Abstract

Visible nulling coronagraphy is one of the few approaches to the direct detection and characterization of Jovian and Terrestrial exoplanets that works with segmented aperture telescopes. Jovian and Terrestrial planets require at least 10-9 and 10-10 image plane contrasts, respectively, within the spectral bandpass and thus require a nearly achromatic π-phase difference between the arms of the interferometer. An achromatic π-phase shift can be achieved by several techniques, including sequential angled thick glass plates of varying dispersive materials, distributed thin-film multilayer coatings, or techniques that leverage the polarization-dependent phase shift of total-internal reflections. Herein we describe two implementations of such techniques: sequential thick glass plates and Fresnel rhomb prisms. A viable technique must achieve the achromatic phase shift while simultaneously minimizing the intensity difference, chromatic beam spread and polarization variation between the interferometer arms. In this paper we describe the above implementations and report on the trades associated with each technique that will lead to an implementation of the most promising one in Goddard's Visible Nulling Coronagraph (VNC).

Paper Details

Date Published: 12 September 2012
PDF: 14 pages
Proc. SPIE 8445, Optical and Infrared Interferometry III, 84452C (12 September 2012); doi: 10.1117/12.926237
Show Author Affiliations
Matthew R. Bolcar, NASA Goddard Space Flight Ctr. (United States)
Richard G Lyon, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 8445:
Optical and Infrared Interferometry III
Françoise Delplancke; Jayadev K. Rajagopal; Fabien Malbet, Editor(s)

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