An Eight-Octant Phase-Mask Coronagraph

We present numerical simulations and laboratory experiments on an eight-octant phase-mask (EOPM) coronagraph. The numerical simulations suggest that an achievable contrast for the EOPM coronagraph can be greatly improved as compared to that of a four-quadrant phase-mask (FQPM) coronagraph for a part...

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Bibliographic Details
Published in:Publications of the Astronomical Society of the Pacific 2008-10, Vol.120 (872), p.1112-1118
Main Authors: Murakami, Naoshi, Uemura, Ryosuke, Baba, Naoshi, Nishikawa, Jun, Tamura, Motohide, Hashimoto, Nobuyuki, Abe, Lyu
Format: Article
Language:English
Subjects:
Astronomy
Coronagraphs
Earth, ocean, space
Electric potential
Exact sciences and technology
Field of view
Light beams
Liquid crystals
Noise reduction
Spectral bands
Stars
Terrestrial planets
Wavelengths
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Summary:We present numerical simulations and laboratory experiments on an eight-octant phase-mask (EOPM) coronagraph. The numerical simulations suggest that an achievable contrast for the EOPM coronagraph can be greatly improved as compared to that of a four-quadrant phase-mask (FQPM) coronagraph for a partially resolved star. On-sky transmission maps reveal that the EOPM coronagraph has relatively high optical throughput, a small inner working angle, and large discovery space. We have manufactured an eight-segment phase mask utilizing a nematic liquid-crystal device, which can be easily switched between the FQPM and the EOPM modes. The laboratory experiments demonstrate that the EOPM coronagraph has a better tolerance of the tip-tilt error than the FQPM one. We also discuss feasibility of a fully achromatic and high-throughput EOPM coronagraph utilizing a polarization interferometric technique.
ISSN:0004-6280
1538-3873
DOI:10.1086/592285