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Proceedings Paper

Demonstrating broadband billion-to-one contrast with the Visible Nulling Coronagraph
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Paper Abstract

The key to broadband operation of the Visible Nulling Coronagraph (VNC) is achieving a condition of quasi-achromatic destructive interference between combined beams. Here we present efforts towards meeting this goal using Fresnel rhombs in each interferometric arm as orthogonally aligned half wave phase retarders. The milestone goal of the demonstration is to achieve 1 × 10−9 contrast at 2λ/D over a 40 nm bandpass centered at 633 nm. Rhombs have been designed and fabricated, and a multi-step approach to alignment using coarse positioners for each rhomb and pair has been developed to get within range of piezo stages used for fine positioning. The previously demonstrated narrowband VNC sensing and control approach that uses a segmented deformable mirror is being adapted to broadband to include fine positioning of the piezo-mounted rhombs, all demonstrated in a low-pressure environment.

Paper Details

Date Published: 11 September 2015
PDF: 10 pages
Proc. SPIE 9605, Techniques and Instrumentation for Detection of Exoplanets VII, 96050K (11 September 2015); doi: 10.1117/12.2189101
Show Author Affiliations
Brian A. Hicks, NASA Goddard Space Flight Ctr. (United States)
Richard G. Lyon, NASA Goddard Space Flight Ctr. (United States)
Peter Petrone, Sigma Space Corp. (United States)
Ian J. Miller, LightMachinery Inc. (Canada)
Matthew R. Bolcar, NASA Goddard Space Flight Ctr. (United States)
Mark Clampin, NASA Goddard Space Flight Ctr. (United States)
Michael A. Helmbrecht, Iris AO, Inc. (United States)
Udayan Mallik, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 9605:
Techniques and Instrumentation for Detection of Exoplanets VII
Stuart Shaklan, Editor(s)

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